In my own Google Reader:

http://josephshoer.com/blog - A Williams grad with great nerdy posts.

http://www.lettersofnote.com/ - awesome historic letters

http://thisisindexed.com/ - webcomic published each morning, 3 second of whimsical humor
http://ephdetour.com/ - Chris, JJ, and Tony baking across Amurika. Chris's writing is great.

http://xkcd.com/ - duh

http://www.boston.com/bigpicture/ and http://www.theatlantic.com/infocus/ -awesome news picture blogs (look at them, you'll understand)

http://www.salon.com/technology/ask_the_pilot/index.html - A pilot talks about the idiocy in his industry. Useful and entertaining.

http://www.ethanzuckerman.com/blog/ - Ethan is a Williams '93 with awesome big ideas.