Gamble Bitcoins
Another great way to earn Bitcoins is to gamble them on selected websites.  These websites DO PAY OUT INSTANTLY when you are winner, so you don't have to worry about receiving your Bitcoins.  Now, please play responsibly : gambling is gambling, although chances are better than at the casino.
MineField   : Win up to 22.5x your bet! - Hot Pick
SatoshiDice : Multiple Bet options.
BestOfBitCo.in : Bet you BitCoins on real life statements.
Bitcoin Advertising
These website will pays it's users to show some advertisement on their website.  It's exactly like google adwords, where users are rewarded when surfers click on the ads.  Very good income if you are running a website that has lots of traffic.
BitcoinAdvertising : Display ads on your website, be paid for clicks.
Anonymous Ads      : Display ads on your website and be paid by the clicks.
Operation Fabulous : Receive bitcoins to display ads from sponsors.