Microsoft has some pretty neat free tools for teachers. In fact, they highlighed a few in a video on their website:
Photosynth - takes your photos, mashes them together and recreates a 3D scene out of them that anyone can view and move around in.
Windows Live Movie Maker - create movies using video or photos from cameras.
Songsmith - generates musical accompaniment to match a singer's voice.
Microsoft Mathmatics - provides a graphing calculator and useful tools to add mathmatical symbols into Microsoft Word.
Bing (and Bing Translator) - Bing is a search engine similar to Google. Bing also includes a translator that can translate text from one language to another.
Interactive Classroom - add in-class polling questions to Microsoft PowerPoint and students can capture notes in real-time via Microsoft OneNote.
World Wide Telescope - enables your computer to function as a virtual telescope bringing together imagery from the best group and space-based telescopes in the world.
Windows Live SkyDrive - store, access and share files, photos, and documents for free online.
DISCLAIMER: As with anything, be sure to check with your IT staff before installing any of these programs on your own.
Click here to watch the video.