Check out Desktop Tower Defense if you haven’t tried it already. It is quite fun and addicting. It is a flash puzzle game whose goal is to stop the enemies (creeps) from getting to the other side of the board by building mazes with different types of towers.
Two places to find it online. The website Kongregate.com has more of a multiplayer aspect to it, because you can chat with other people on the website after signing up for an account. The other place is the author’s home page, handdrawngames.com.
If you do try it out and get a decent score playing at least the Medium difficulty you can save your score to a group of other people. My friends and I have been saving our scores under the group name “llbbl”. Feel free to add your scores to that group. You can see our group and other group scores here.
this game rocks