Go to the home center and buy the ceramic tile cutting bit for a Roto-Zip. If you buy the small size, you can put it in a Dremel. I have cut a bunch of tile this way. It's a little dusty but you will be able to cut a lot faster than you expect to be able to. This is for wall tile.
For floor tile, they are fired at a higher temperature and are MUCH harder. You do have to cut these with diamonds.