Here are a few of the popular free bitcoin sites/faucets donation addresses. Please feel free to donate to support the Bitcoin community.
 
DailyBitcoins: 16RTcfQi1M2gXExXHus4pbNYbSZLr5dQoS
BitcoinFaucet: 13mNaTQ45fpPA12LCFgyKoeY64AAoK7uHt
BTC 4 U: 1GbXVsjhhfdyq5TjsKRTxBbGGb4k5AQHrn
Bitcoins4me: 18CXPM4JgKAWzLZDJMJDetrpvAW7nyHLJi
Can Has Bitcoin: 1918aivQtnwMediJen1GoS5yXDHXhoPoVq
Bit Crate: 1LSFZT3aK2Rxqoz1Jts8RfLQZoQenz4W2c