Litecoin, doge, dash - low to medium risk
other unknown cryptocurrencies - medium risk
Ethereum, Maidsafe, siacoin, monero, storjcoin, has good prospects.
But how do we invest our precious Bitcoins? I don't want to hold them in wallet. I want to earn interest.
To earn interest you can buy Coinomat Shares at poloniex
https://poloniex.com/exchange#btc_cnmtPays weekly interest.