Online Encyclopedias
Other
Education online history site in the UK
http://www.freerepublic.com/focus/f-news/873496/posts - Maps of Iraq
Dictionaries etc.
Merriam-Webster's online language tools
Unit conversions (metric to English, etc)
Computer File Formats
What Is.COM's list of every file extension known. That's what they say. Descriptions are sketchy at best, incomplete or wrong at times (ACL = Corel Draw 6 keyboard accelerator file? Maybe, but how about Access Control List? Jeez.)
There's lots of other interesting info on the main Whatis.com site.
The descriptions are more complete at Wotsit.org and quite a few of the file format entries include links to detailed format info. And alas, the site has some *really* annoying ads and popups. The price we pay ...
Computer Hardware
Ars Technica
CDs, DVDs, Specs
http://bmrc.berkeley.edu/people/chaffee/jolspec.html