Uhhh I have all my important files on the external hard drive, and I like to keep it organized.
Basically
Anime (Most stuff in there is real anime, but I have some TV series in there too like Goosebumps or Eerie Indiana)
Downloads (All the stuff that comes from Limewire, uTorrent, or w/e. I put it in a different folder when it's done)
Movies (All non-anime movies)
Games (All types of games, roms, dos games, pc games, etc etc)
School (All my school stuff)
Graphics (Everything graphical. Avatars, signatures, wallpaper, pictures, everything goes in here)
Music
RPG Maker (RPG Makers and projects, RTPs)
Tutorials (I keep tutorials for most Adobe programs here, and 3DsMax)
That's pretty much it. Simple and clean.