Physics

The PhET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations.

Great guide to physics news, information, and links.

Wolfram Alpha is a computational knowledge engine or answer engine developed by Wolfram Research. It is an online service that answers factual queries directly by computing the answer from externally sourced "curated data", rather than providing a list of documents or web pages that might contain the answer as a search engine might.