Wikipedia.com is a great source to retrieve information on anything your heart desires.
Support.Microsoft.com has a data base that covers pretty much every question you'll ever have about anything to do with Windows and its associated software.
Download.cnet.com is a great place to download free software (anti-virus software, media players, internet browsers...)
HowStuffWorks.com is a awesome site for the curious minds.
Health
Health.com has answers for any question you have to do with your health.
Menshealth.com is for the men!
Dictionaries
I find the google dictionary to be the fastest. I'll add more as they come.
