I know I'm not alone in wishing there was a TimeSnapper equivalent for the Mac. Among many things it lets you look back in time at what you were doing on your computer minutes, hours or days ago.
Perfect for remembering what you were doing yesterday, and even to recover stuff that was displayed on your screen.
Inspired by TimeSnapper, I've created a small bash script that I've called MacBlackBox which takes regular screen-shots every few seconds. Every hour it combines the screenshots into an mp4 video, and every day it combines the hourly videos into daily videos, one per screen.
It is available in GitHub here. Happy to accept improvement suggestions.