http://robozzle.com/
You need silverlight installed to play the game.
Small preview by the creator:
Your object is to program the robot to pick up the stars on each puzzle in order to complete them, using a simple set of commands. Turn, forward, paint color, call function, and each can be conditioned by either a red, blue or green field.
I guess it's not a unique gameplay concept, but the interface is pretty simple and quick. It's a bit more than an average flash-game puzzle and i think it deserves it's own thread.
You don't need to complete certain puzzles in order to play the rest and making an account (very simple and quick) let's you track your completed puzzles as well.
There's alot of puzzle both easy and hard, and new puzzles are constantly created.
I figured some of the clever people here would enjoy the game.
I'm personally somewhat stuck in the campaign around page 9, with 2 exceptions earlier, and I have yet to complete a puzzle with more than 3½ in rating I think, so I'm not really good at even, though i enjoy some of the new puzzles so I'm still playing once in awhile. I'm too stubborn to get help for some of the puzzles that I can't complete.
Note: please don't spoil full solutions. Spoilered hints are ok.