I always give myself at least two partitions...
one for the operating system and programs and my desktop (where I keep tons of stuff)
The other ends up being a dumping ground
eventually it's cleaned out... but for the most part it's just storage space.
The benefit is that I can completely blow away my OS install without touching the other files. In my current setup I have my pictures folder aliased there, my music folder, fonts, and a few other things. After that it's just TONS of files.