You may not be aware that the MilkyWay@home project has announced that they need $20,000 in order to keep the project going.
You can help the "cause" by checking this page and donating any bitcoins you have or earn:
http://www.bitcoinutopia.com/2014/07/milkywayhome/
If you want to mine Bitcoins, then ideally you need a USB ASIC device, which cost £10-20 (off eBay or Amazon).....or you could spend (say) £70 or even $400 on a dedicated miner.....and some cost a lot more

Then just download the cgminer Campaign #3 WU's and you'll be helping MW with your donation.
Note: Bitcoin Utopia take a 12% "commission" for whatever you earn...but at least the other 88% goes to MilkyWay

Of course, rather than buying an "miner", you could, instead, just make a donation to MilkyWay

EDIT: The Bitcoin Campaign #3 runs until mid-October 2014. So in order to help MW, please join in sooner rather than later

regards
Tim