http://www.handdrawngames.com/DesktopTD/

This is a fun little Flash game. Build a maze of towers to stop the creeps from getting across your desk. It gets pretty frantic as you go up the levels, and you'll need a smart set-up to beat all 50 on Medium difficulty, let alone Hard. Submit your high scores to the scoreboard "EoFF" and we'll see who sucks the least.