If you’re like me and have about 100 files sitting in your Safari downloads folder, have a look at DownloadComment:

When you download things in Safari, DownloadComment will put the original URL into the saved file’s Finder Comments. Now you’ll always know where your downloads came from.

Cmd-I in Finder to display the file comments, and BAM! Instant reminder where on earth you got that file from and why. I’ve been using it for less than a week, and it’s already proven itself useful.