Signature campaigns are obviously the most successful way to make money here.

However, there are many ways to earn Bitcoin which aren't linked to the forum.

Here are a few ways off the top of my head.

Trading (Requries Bitcoin to start)

You can activly buy and sell Bitcoin at Bitcoin exchanges, buy low and sell high is the key.  High risk, but often high rewards.

Bitcoin Faucets (Free to start)

Bitcoin faucets release free Bitcoin each day or hour, it depends on the faucet.  You can gain Bitcoin by doing this, but they pay very low.

Gambling (Requries Bitcoin to start)

Sites like primedice and satoshi bet allow you to gamble your existing Bitcoins to try to gain more.  Very risky, ant often not worth it.

Working for Bitcoin (Free to start)

There are now websites which you can use to earn Bitcoin by doing freelance work.  See my signature (cryptogrind) for a link to a fiverr like website where you can list services in exchange for Bitcoin.

There are many other ways to earn Bitcoin, but these are just a few.

Hope that helps.