Mac Gems: Hazel 2.3
OS X's Folder Actions are a nice idea, but not always so great in execution. Hazel takes the same concept, of automatically applying actions to items in folders, and makes it both simpler to set up and more powerful.
http://rss.macworld.com/click.phdo?i=4d2c7b7d95317dc371dae5daba9cb4fb