Originally Posted by Big Dave
If you need to trim a little off of a peice of wood then I would recommend a small hand plane
I'd second this advice. Using a belt sander for fitting joints is like using a blender to peel a potato.
If you want a general purpose sander, get a Random Orbit 5" palm sander. I too like the porter cable model.
For trimming joints, get a chisel, and a block plane, and learn how to keep them sharp. It's much quicker, more accurate, and infinitely more pleasant than using a sander to remove wood.