UCI - Cycling's worldwide governing body.
Bill's Cycle Racing Results and News Service - Good Pro racing news and results site.
Bertil Odling's Results site - results a bit quicker than Bill's site, but not as much other news, but both Bill and Bertil tend to get their news from...
Yahoo News (Cycling) - but this can be a bit slow to load, and only very recent results remain
Bicyclopedia - an online reference book covering lots of cycling and bike related stuff.