There are so many of these that I have divided them into categories. Those that don't fit neatly anywhere else you can find here, including...
Meadow Creek Dairy, my home.
The CDR, a database of articles and opinions from the members of Culture List. Even if you aren't mad enough to be a member, you should check out this collection.
The Seti At Home Project, an opportunity to aid the Search for Intelligent Life with your humble desktop computer. Who needs flying toasters anyway?
Interactive Fiction is an art form that interests me enough that it will one day have a page of its own around here, but for the moment I'll content myself with pointing you to the archive, Baf's Guide to the archive, and the yearly Interactive Fiction Competition.