Here are a couple of Mac App Store apps gone free.
Prices are subject to change at any time.
SCOtutor for Mac – A beginners video tutorial guide to using a Mac. (Normally $3.99)
SkySafari shows you 46,000 stars, plus 220 of the best-known star clusters, nebulae, and galaxies in the sky. (Normally $4.99)
Optimism is a mood chart app that helps you develop strategies to manage depression, bipolar or other physical and mental health conditions. (Was $24.99)