Updated post:

Edited minimum deposit to 0.1 btc.

Website link is at http://www.9988ft.com/

You may try it out via the following userid and password.

Userid: 34FNTrial
Password: Bitcoin1234

Website reviews e.g.
http://www.galaxy388.net/option/mod_content_article/cid/5728
http://www.90agency.com/gamingnews/winningft-sportsbook-review/

Bitcoin Sports Betting now available.
(1) Both live and scheduled sports betting available
(2) Wide range of sports - from soccer to baseball, from basketball to ice hockey, from boxing to Formula 1.
(3) Cash in/cash outs at any time.
(4) Minimum deposit of 0.1 btc. *EDITED*
(5) No minimum amount for withdrawals.

Website link is at http://www.9988ft.com/

You may try it out via the following userid and password.

Userid: 34FNTrial
Password: Bitcoin1234

Website reviews e.g.
http://www.galaxy388.net/option/mod_content_article/cid/5728
http://www.90agency.com/gamingnews/winningft-sportsbook-review/

For a trial account or deposit/withdrawal enquiries, please PM.

I used to wish I could buy real-world stocks and keep it denominated in btc.

E.g. APPLE stock in BTC instead of US$.

And then I found Keza.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

It is really hard to predict the tops and bottoms.  I think a better approach is to keep a longer-term investment programme, regardless of the ups and downs. 

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

I save all my idle coins and let them grow safely in real-world investment porfolios (that are denominated in BTC).

This is not high-yield investment programmes (HYIPs), as I think those are too risky.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

To trade effectively, you have to be able to understand the relevant indicators e.g.
RSI
Bollinger bands
Short term MA vs Long term MA
Moving Average Convergence Divergence (MACD)
Etc

Study carefully, invest small amounts at the start.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Bitcoin is already a global currency. You can earn it, spend it, save it, invest it.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

I would hold it and keep it invested. You can grow your btc while linking it to a real-world index e.g. the S&P 500.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

BTCJam has too many defaulters, hence the sharply reduced volume on the site.

Would recommend other avenues to invest and grow your btc.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Nurture your 1.5 btc. Save and invest it, and let it grow steadily.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Bitcoin's future is bright, especially when it is integrated into the real-world economy.

Invest globally with bitcoin. Wealthfront for bitcoin.
http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

You can actually invest in Apple with bitcoin, as part of an indexed portfolio investment. Apple makes up part of the S&P500 index within their index products.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account

Don't sell your bitcoins (or other coins). Save them well.

I am saving my bitcoin in real-world investment portfolios via Keza. Keep your bitcoin, let it grow steadily.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account

(1) I agree with the previous poster.  Do not commit all your funds to bitcoin.  Decide on a percentage.  Diversify.

(2) Even for the portion you commit to bitcoin, spread the investment depending on your investment horizon & risk/return appetite.  All investments carry risk - you need to balance that risk/return profile.

For bitcoin investments, you can consider 3 different strategies e.g.
(1) High risk, high return short-term trading strategy ("buy low, sell high"): But can you read the market well enough to generate the best trading strategy? For every buyer of a coin, there is a seller, so who is doing it wrong?
(2) Moderate risk, moderate return portfolio investment strategy e.g. Keza (http://www.getkeza.com) as an investment platform.  But you need to invest time in selecting the right investment portfolios based on the composition, underlying beta and future outlook.
(3) Low risk, low return secured lending strategy (collateralised lending).  But need to vet borrowers based on past track record too.

I would avoid HYIP, Ponzi schemes, and grandiose promises.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Recognise that trading is a strategy which requires a lot of attention to market movements.  There are many good exchanges (bitfinex, bitstamp, itbit, poloniex).  Consider if you can read the market well enough to generate good returns.

Learn how to read indicators e.g.
Short-term SMA vs Medium-term SMA
RSI
MACD (Moving Average Convergence Divergence)
Fibonacci lines

Also consider alternatives for your bitcoins e.g.
(1) Moderate risk, moderate return portfolio investment strategy e.g. Keza (http://www.getkeza.com) as an investment platform.  But you need to invest time in selecting the right investment portfolios based on the composition, underlying beta and future outlook.
(2) Low risk, low return secured lending strategy (collateralised lending).  But need to vet borrowers based on past track record too.

Avoid HYIP, Ponzi schemes, and fanciful, unrealistic promises.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Investments for your bitcoin can generally be separated into several categories.

(1) High risk, high return short-term trading strategy ("buy low, sell high"): But can you read the market well enough to generate the best trading strategy? For every buyer of a coin, there is a seller, so who is doing it wrong?
(2) Moderate risk, moderate return portfolio investment strategy e.g. Keza (http://www.getkeza.com) as an investment platform.  But you need to invest time in selecting the right investment portfolios based on the composition, underlying beta and future outlook.
(3) Low risk, low return secured lending strategy (collateralised lending).  But need to vet borrowers based on past track record too.

Avoid HYIP, Ponzi schemes, and fanciful, unrealistic promises.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

When it comes to managing money, I would advocate the following:

In your 20s, the reality is that bills to pay would make up a large part of how you spend your money. Save 10%, invest 10%.

In your 30s and 40s, investing should increase as you build up your investment component. Invest 30%, save 10%.

Then in your 50s, investing and savings dwindles as you prepare for your twilight years.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

Save your bitcoins, grow it carefully. Nurture it. I would invest the bitcoins in real-world investment instruments like mutual funds and indexes. You might want to check out Keza. Their platform allows your bitcoin to remain denominated in bitcoin but you get to invest in global portfolios like the S&P500 index.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

I think the discussion on the best investments, depends on our definition of what "best" is.

Investment returns will generally be correlated with risk, so:
(1) High risk, high return short-term trading strategy ("buy low, sell high"): But can you read the market well enough to generate the best trading strategy? For every buyer of a coin, there is a seller, so who is doing it wrong?
(2) Moderate risk, moderate return portfolio investment strategy e.g. Keza (http://www.getkeza.com) as an investment platform.  But you need to invest time in selecting the right investment portfolios based on the composition, underlying beta and future outlook.
(3) Low risk, low return secured lending strategy (collateralised lending).  But need to vet borrowers based on past track record too.

I would avoid HYIP, Ponzi schemes, and grandiose promises.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)

I think BTCJam is shrinking in size. They have restricted US lenders/borrowers.  Pretty quiet nowadays due to the number of defaults.