I've always found it hard to remember where stuff on my system came from. I download a large amount of stuff, and keeping track of it is a real pain. On Mac OS 9, the origin of a downloaded file used to be stored in the Finder's Get Info comments. Recently I discovered the Download Comment extension for Safari, which restores this functionality for Safari. Unfortunately, I don't use Safari as my primary browser (I do use it as a secondary browser -- yeah call me crazy). At the moment Firefox is my primary browser because of the ability to save groups of tabs of bookmarks, the tabbrowserextensions plugin and the excellent Adblock plugin. Unfortunately, I'm stuck on Firefox 0.8, because that's the last working Firefox, tabbrowserextensions setup that I could get to work. I haven't tried the Firefox 1.0PR, but probably will this weekend.

Also, I have delicious category for delicious hacks, which includes useful/interesting tools that work with del.icio.us.