Classic Computer Games:
Bounty Hunter - you're hunting for an escaped prisoner
Magic Squares - Move the boxes so they read 1-8
Pong - Similar to the classic "blocks" game.
Reflex Game - see how fast your reflexes are
Slimewars - Star Wars parody
Blackjack - see who can get the highest number under 21
Hangman - current topic is "Presidents of the USA"
Magic 8 Ball - see what it has to say to your questions
Paper Rock Scissors
Peg Solitaire - try to get all but one peg off the board
Tic-Tac-Toe - 4 levels: very easy, easy, average, and hard.
Towers of Hanoi - stack the disks in order from largest to smallest - sounds easy, but it's challenging
Typing - see how fast you can type
you can download one that does for free at Net 1000.net > Software Downloads.