The downloads folder on a Mac can get pretty messy, but MacWorld shows off an automator script that automatically keeps that folder organized and clean.
Chances are that the bulk of your downloads fall into one of a few different categories: videos, images, disk images, or archives. With MacWorld’s workflow, you can set it up so every time you download a file it automatically gets organized into whatever folder you choose. Of course, you can also do this with software like Hazel, but the Automator script is free and built right into OS X. Head over to MacWorld for the full guide.