Some of my favourite sites are listed here. I strongly urge you to visit them.
 

Hilarious -- have a clean pair of pants ready.

http://members.shaw.ca/nerdfactory/
The personal webpage of Stephen Tao.

http://www.flatface.net/~kithkin/
A wonderful assortment of artwork and ramblings like only Kithkin F. Avrien can deliver.

http://www.stepmania.com/ & http://www.ddruk.com/
The two best resources for everything you'd ever need to practice DDR at home.  Free registration is required at turtleddr.

http://www.tvtome.com/
A wonderful resource for everything you ever needed to know about your favourite TV shows.

http://www.coolmath.com/graphit/
A very handy graphing calculator; useful for checking if those "sketch the graph of..." questions are done right.  Although, it does have one issue with drawing rational-powered functions.

http://www.sing365.com/
What I would consider the best overall resource for finding information on an artist, in terms of bios, albums, release dates, song titles, and lyrics.

http://www.tgtsoft.com/ & http://www.wincustomize.org/
Two great sites for Windows GUI renovation.  Everything from cursors to wallpapers to new visual themes.  I update my wallpaper every month with something from wincustomize.

http://www.fanstuffs.com/
Great PPG fanart as well as anime fanart.  Some of my artwork can be found at this site.