Here's a couple of web based games that I wrote many years ago. They are all pretty naff (well, the sliding block puzzles are quite good). If you prefer games with a bit more action, you could try out the downloadable games in the Software section.
Move the wooden pieces around a board. Sounds easy, but is very hard!
Inspired by a games machine in a pub. Clear the board by making words.
A friend of an ex showed me this board game. It's an interesting take on Noughts and Crosses. It's a two person game... One day I may get round to writing an AI so I can play against the computer.
Stuck on a crossword clue? Already got some of the letters? Then you could cheat...