You could spend it on purchasing mining contracts. I have stuff going on at Cryptsy, BCS, PBMining, and Scrypt.cc should you want to check those out.
I'm going to shamelessly post my referral links to them, because why not?
Cryptsy - Online exchange site where you can buy and sell Bitcoin and altcoins. They also have a Mining Contract 'currency' that are essentially mining shares you can buy and sell with Bitcoin. Every day, based on your shares you're accredited Bitcoin. You can also buy the shares and sell later when prices go up.
Bitcoin Cloud Services A service I'm trying out, seems to pay in BTC daily. Five year contracts (legitimacy isn't guaranteed. Then again, the market of trade is never guaranteed) and the BTC is deposited to your wallet
PBMining is another service like BCS, but has a smaller minimum contract requirement, and pays weekly.
Scrypt.cc is like Cryptsy's Mining Contract shares, but mines the most profitable altcoin and autotrades to BTC.
^those are handy for if you want to toss them somewhere and let them build up.
Another thing to do is to watch the values of altcoins on Cryptsy, buy them when the value of altcoins go down, and sell when they go up. You can profit from that. There are other exchanges besides Cryptsy, but I like using Cryptsy.
And another way is to sell Bitcoin for your fiat currency when it spikes in value, and buy when it drops. There are a lot of ways you can do stuff.