Another good online time-waster: a version of Breakout that actually manages to put a new twist on the game by giving it a circular playfield — Plastic Balls.
Rather than running your paddle back and forth across a plane…well, you know those bright yellow plastic funnel coin collectors where you drop a coin down a trough and watch it go spinning in circles down the funnel? Put bricks around the outside edge of the funnel, put your paddle rotating around the funnel, and let the ball bounce between your paddle in the center and the bricks on the outside.
Very cool, and the extra level of pseudo-dimensionality adds a nice new touch to the gameplay.
(via Collision Detection)