minimalmac:

Simply put, Hazel takes the idea of mail rules and applies them to the entire system. At its core, Hazel is a watchdog. You tell it to keep an eye on a folder, and if certain criteria are met, perform an action. We’ve covered Hazel before, but I wanted to focus specifically on combining it with Dropbox.

Hazel is one of those apps I need to eat my own dog food on and spend a few minutes a day learning something new about. It can be amazingly powerful, and save a ton of hassle and time, especially when combined with other tools. That said, every time I read a post like the one linked above I have one of those “Holy crap!” moments of how I can put it to better use.