Jezzball
Jezzball is available on several websites in Java. In Jezzball, you have a square box with balls bouncing around in it. You must corner the balls without them hitting and breaking your partially formed walls. It is a very simple game, but it can be addicting.
Bomber Bob
This is a very simple war game. You are a fighter aitplane, and you must shoot down scores of enemy planes before they sink your ship, and without being shot down yourself. This game is a flash game.
Literati
This is Yahoo's free version of Scrabble. It is scored slightly differently, but overall, it is nearly identical. Literati is Java based and requires a free Yahoo ID.
Diesel and Death
This is another flash game. This one is a dirt bike racing game. Very simple, but entertaining. You race against a computer controlled bike.
Helicopter Game
In this simple yet very challenging game, you must use one button on your mouse to navigate your helicopter through the cave without crashing it. The cave is complete with obstacles, drops and climbs. Wow. This game could be very addictive! Game is built with flash.
Curve Ball
This is an adapted ping pong ball game. You are in a square tunnel with a computer controlled opponent at the other end. The key is to get the ball to bounce or curve, and get past your opponent.
Overkill Apache
Similar to Bomber Bob, but this time you're flying an Apache helicopter over the desert. Your enemies come from all directions, too! Some good simple fun, though the game needs more controls.