CEX.io - Bitcoin Commodity Exchange
The first commodity exchange to trade GHS (GigaHash per second) of their mining equipment. You earn Bitcoin based on how much GHS you have in your account. They also sell BitFury chips and futures contracts.
FinMutual lets you invest anywhere from $25 to $999 and you can get 1.8% to 2.6% daily, depending on the length of time. Best of all, they accept Bitcoin!
Cryptsy is an excellent site where you can trade in virtually any cryptocoin available!
Pyramining - Invest some Bitcoin and make a profit over time!
Cloud Hashing - A new Bitcoin investment site.
Cointripler - Another new Bitcoin investment site. Triple your Bitcoins in 20 days, starting at either 0.01, 0.05, or 0.2BTC.
FlatBitcoin - A Bitcoin investing site which lets you invest 0.5-10BTC over a week and get a 5-10% return.