alpinetech. Collection of many search engines on the same page.
Google.com. Best search engine.
Search Engine Watch compares search engines.
Ditto.com searches for images.
Searchable index to articles in American Journal of Physics and The Physics Teacher, 1970-1998.
Scientific American's Frontiers. TV show and resources.
NASA. Searches all NASA sites.
Scientific American. Articles on-line. "Ask the expert". Searches those answers as well as the magazine.
Bulletin of Physics News, from American Institute of Physics. Also, see their archive of graphics.
Ask A Scientist. An archive and a search engine of hundreds of questions answered by Argonne National Lab.
Search several newspapers and TV channels for current science stories. By Lawrence Berkeley National Lab.
ScienceCentral. Search the web or journals or receive emailed stories of your choosing.
TIPTOP, by Physics Web. A good search place for physics web resources.
The Skeptics Society has articles debunking pseudoscience.
Physics World. Search, links, short news articles from Physics World magazine.
Physics Surf. Links for resources, media, etc. By the US Air Force Academy.
Eric Weisstein's Treasure Trove of Physics. Search alphabetically or by word.
Education World.com's search engine.
Donald Simanek's Pages. Compendum of useful and humorous links.