I am not really a fan of normal Tetris. But there have been a few versions lately that are a bit more interesting. First is Human Tetris, which looks kind hard:
(You can see more of Human Tetris here.)
Another version of Tetris looks very easy and times, and very difficult at other times:
Finally, here is a version of Tertis that you can actually play at your computer. It is called Diggtris and it uses stories from Digg to make the bricks that fall. The amount of Diggs a story has determines the size of the piece, and the category that the story is in determines it's color. Check it out.