My system is complicated, but works for me
When I download and unzip supplies, I change the folder name to "KitName-DesignerName-website". Then I add a subfolder inside with the same name and move the previews, tou's and any 'no-piracy' or similar graphics into it. The the whole thing goes into a folder on my computer. When that folder gets close to the capacity of a DVD-R, I seperate the subfolders out and have adobe automate a set of contact sheets. Then I put those subfolders back into their original folder, add the contact sheets to the main folder, and record the whole thing to a DVD. As soon as I have verified that the DVD recorded properly and printed off the contact sheets, I delete the original files from my hard drive.
Then those contact sheets go into a large binder with divider tabs between each disk set.
I'm not sure if this is helpful or confusing, but that's how I do it. Right now I have 8 DVD's and the folder for #9 is almost full. I have been collecting kits and freebies since Dec '05, and starting about fall of '06 I started being more selective about the freebies that I download.
I *would like* to create some sort of indexing system, that way if I'm looking for a fuzzy fiber or a purple tag, I don't have to look through binders of contact sheets.