Hey, I'm the masters of partitions!
1.5 GB for OS9
1.5 GB for OSX
4 GB for software only divided in to sections:
-Audio: Protools, Digital Performer, iToons (do not storage the songs in here), etc.
-Publishing: Photoshop, M$Office, Illustrator, the scanner stuff, etc.
-Tools: Norton, Toaster, Stuffit, etc.
-Video&Animation: Final Cut Pro, Media Cleaner, After Effects, etc.
-Web: Dream Weaver, Flash, Hotline Client, Comunicator, Explorer, etc.
Then, a 4th partition (for thouse who doesn't have OSX would be your 3rd) called "Storage" that would take thje rest of the hard drive. Here is where you are gonna place everything, pictures, documents, movies, mp3, downloads, etc. Your primary scratch disc will be too.
Why is that? because the use of files would lead to fragmentation and later would crash the softwares. The partition "Storage" would be the only one fragmented and would be the first one with a virus in case you get one, leaving the rest of the partitions alone.
It is the best way to organize the computer, at list for me works fine. I do not remember when I started to do it like this, may years ago.
It workd too when your computer is accesed by others in your family. They just wont mess around with the soft because they do not have to touch them.
Another good trick is to place an alias of the "Soft" partition in the Apple menu items, so you can have a direct acces to your soft.
This is long way better than droping files togatehr with the soft and the OS.
Note: If the hard drive is 20GB the "OS" should take 1GB, the "Soft" 5GB and the "Storage" the rest. That is the way I have mine, the same thing with my powerbook that has a 10GB drive.