On the other end of the spectrum, I've got a netbook with:
4GB SSD for the system drive (2.7GB used), and a
16GB for the data drive (4.4GB used),
20GB total avail, ~ 7.1GB used. That includes ~ 1.3GB of photos, but not many other docs.
Despite this small size, it is fairly well equipped. Ubuntu 10.04 OS, and I've got a few simple games, a photo manager, scanner app, a couple browsers, Skype, TeamViewer, OpenOffice, Audacity sound editor, a music jukebox app (like iTunes), WINE ( allows some Windows programs to run), Google SketchUp (3D modeling program), plus the system and admin apps.
It runs all those pretty well.