Hazel

I was just in the process of writing a Mac OS X automator to delete all the files in my downloads folder if they are over a week old (one of the Productive Programmer samples) when I found this: Hazel. It's a cheap-ware preference pane plug in that allows you to set up rules (kind of like a mail reader) for folders and maintenance tasks. I just set up a rule that deletes all downloads that are over a week old (I'm terrible about downloading stuff, unzipping and installing it, but forgetting to get rid of the downloaded archive).

Looks pretty cool, costs $16, and has some nice configuration options.