My favorite site for free online flash arcade games is Challenge Arcade. They have a huge number of games and they add new flash games nightly. This is a great site for shooting games, puzzle games, and some unique off the wall stuff. Another site that I like is addictinggames.com. They have a bunch of cool games too. They have a nice collection of free downloadable games if you're into that kind of thing. The best thing about both of these sites is that all of the games are free to play! Try out Buggy Run 2 or Biff and Baff if you are looking for something fun to waste away a few hours with.