Kalam Labs - Twitch for Science
DragonBox Numbers - Teach kids about numbers with an easy and fun game
RunaWFE - RunaWFE Free is a free Open Source BPMS (business process management system), which serves to optimize and automate business processes (for Windows, Linux, Mac OS).
Wikids - An encyclopedia that talks to your kids
Litnerd - The Pixar for education, reading program for K-5 schools
Four Seconds - A timer and a simple rule: stop it at exactly four seconds.