Up till now I know two websites where one can get free bitcoins:
Is there a comprehensive list of all such websites available somewhere?
Constantly updated list: https://bitcointalk.org/index.php?topic=90718.0
Free Bitcoin sites:
The Bitcoin faucet. One time payout per Google account. Explanation available at the site.
Daily Bitcoins. Can be used once an hour now, and not just once a day.
CoinAd.com. Can be used once an hour with registration.
Bunny Run. See here for more info.
Free bitcoins - netlookup.se
Nakabot's Bitcoin Faucet (Tor hidden service) NakaBot pays out a portion of its winnings in 0.001 increments.
Free BitCoin Daily Scratchcard
kickme.to/goxkeygen MtGox account needed to redeem the code one receives.
bitcoinpixels.com 0.01 BTC free when signing up to betfair. See here for more info.
memorydealers Learn how here.
Omnicoins Learn how here.
bitcoins.so * Roll dice : same numbers - win 0.01
Paperco.in faucet * Scan a QR code to reveal a MtGox code for 0.0007 BTC.
Dragon's Tale A casino site, but gives out small amounts for free that you can use to gamble with or withdraw to your own Bitcoin wallet.
Seals with Clubs Seals has a free poker tournament every hour with a .05BTC prize. There are larger free tournaments from time to time. See here for more info.
Strike Sapphire See here for more info.
BitVisitor Earn Bitcoins for visiting websites
CoinTube.TV Earn Bitcoins for watching TV
You can also check out this site: http://earnfreebitcoins.com
EarnFreeBitcoins.com is a website in which you earn small amounts of Bitcoins in exchange for visiting websites for a designated period of time. You may be required to spend anywhere from one minute, up to five minutes or more on the sponsored website. You must spend the full amount of required time on the website in order to recieve payment.
http://skude.se/BTC/ provides links to a number of websites that provide free bitcoins, but generally doesn't include sites it doesn't get a referral bonus from. It also provides a timer that helps you determine when you can revisit each site to collect more.
Another site providing a good list in a readable format is here: http://bitcoiner.net/list
And here you get paid up to 4 mBTC for viewing websites for 5 minutes http://www.bitvisitor.com
Most of those websites don't give free bitcoins anymore. The only updated daily list I've been able to find is at the end of any post of the blog http://thebitcoinmaster.blogspot.com