O'Reilly online:
http://www.oreilly.com/openbook/
Computer books and manuals:
http://www.adobe.com/products/acrobat/webbuy/freebooks.html
The Network Book:
http://theory.lcs.mit.edu/~rivest/crypto-security.html
FreeBSD documentation:
http://www.freebsd.org/tutorials/
http://techpubs.sgi.com/library/tpl/cgi-bin/init.cgi
IBM Online Redbooks:
http://www.redbooks.ibm.com/
Programmers reading:
http://www.programmersheaven.com/
Programming Pearls 2nd edition:
http://www.cs.bell-labs.com/cm/cs/pearls/
C stuff:
http://www.strath.ac.uk/CC/Courses/NewCcourse/ccourse.html | http://www.cprogramming.com/tutorial.html
Lisp stuff:
http://www.cs.cmu.edu/afs/cs.cmu.edu/project/ai-repository/ai/html/cltl/mirrors.html
Handbook of Applied Cryptography
http://www.cacr.math.uwaterloo.ca/hac/
X Window System
http://tronche.com/gui/x/
Misc programmers reading
http://www.ic.arizona.edu/~nromano/spring99/readings.htm
http://www-03.ibm.com/ibm/history/
Electronic Publishing
http://www.civeng.carleton.ca/~nholtz/ElectronicPublishing.html
Digital processing
http://www.dspguide.com/pdfbook.htm
Books and texts
http://digital.library.upenn.edu/books/
Medieval history
http://www.fordham.edu/halsall/sbook2.html
The Dead Sea Scrolls
http://lcweb.loc.gov/exhibits/scrolls/toc.html