whatis.com - Great site for help on IT terms and meanings.
w3.org - World Wide Web Consortium - specifications for web technologies.
iana.org - Internet Assigned Numbers Authority - site for coordinating assignment of IP addresses, port numbers, etc...
registrar.verisign-grs.com/whois - Determine information about domain, registrars, DNS servers.
internic.net - Determine information about domain, registrars, DNS servers - the original site.

Third Party Support Sites:

support.microsoft.com/default.aspx - Microsoft Knowledge-Base and other help.
support.novell.com - Novell Support

Useful:

bandwidthplace.com/speedtest - Check the speed of your Internet connection.
maps.yahoo.com/py/maps.py - Map site - great for finding directions.
timeanddate.com/worldclock - Help with Timezones.

Shareware:

download.com.com - One of the largest and best.
downloads-zdnet.com.com/2001-20-0.html - Another large and excellent site.
32bit.com - Great site with a lot of software.
thefreesite.com - Mostly everything is free.
 

Entertainment:

terraserver-usa.com - See aerial photographs of where you live or work.
Asteroids - Remember this old Atari game?
Chess - Good web page chess game.
P-Man - Eating dots and watching out for the bad guys.
Tetris - Blocks falling game.
Tic-tac-toe - Try to beat on level 3.