Be sure to visit the Sheldon Brown memorial for your comments. People are also leaving comments at Sheldon Brown's MySpace page as well as his Facebook page. Harris Cyclery says a memorial service will be scheduled for March. I'm sure it will be huge.
One of the best obituaries I read came from Sheldon's friend John Allen, who is himself a very well regarded cyclist advocate in Massachusetts and a director at the League of American Bicyclists. Chico Gino posts Allen's words at his blog. Rich Kelly recounts his personal encounter with Sheldon Brown at Interbike, including some great photos of Sheldon proclaiming "IT'S ALIVE!" when asked about 3 speed internal hubs. Jenna Wortham mentions Sheldon in the WIRED blog yesterday, with links out a couple of other blog mentions (among hundred posted this week) and info about a planned memorial ride.
Here's a badge from Chico Gino who was inspired by Jim G (click on the image for different size options):