For my Desktop its
800x600

For my Notebook its
1024x768

This question has been asked a lot lately...

http://www.webhostingtalk.com/showthread.php?s=&threadid=28536
http://www.webhostingtalk.com/showthread.php?s=&threadid=27871

I'm still using 1024x768 though on my little 13" monitor though. Hopefully I'll be getting a new monitor for Christmas.

http://www.webhostingtalk.com/showthread.php?s=&threadid=24404