You can learn about bitcoin here: http://www.weusecoins.com/ and you can purchase bitcoins on ebay or on these sites: https://mtgox.com/ ; http://bitmarket.eu/ ; http://tradehill.com/
How does it work (long story short):
1) download the bitcoin client from http://bitcoin.org/
2) after you run it, you will see that you were assigned a new address (it's your private address, like private bank account)
3) buy bitcoins through one of the sites listed above (or other)
4) when you receive bitcoins on your address (bitcoin account), you can send any amount to my address: 1N8jdD34mEs5Svwuj5zSYfxYDeJc2HQ3sN
6) you are now a proud donor
Please note that donations won't give you any activation keys for faceniff or other apps.