Great resource for every contester - http://www.contesting.com
Know exactly when every contest is. There's a contest nearly every weekend!
WA7BNM's contest calendar - http://www.hornucopia.com/contestcal/
SM3CER contest service (lists more obscure European contests): http://www.sk3bg.se/contest
Can't wait a whole year for the contest organizers to check logs and figure out who won?
Get the latest claimed scores, as well as the juice on who ran Europe and JA like a bat out of hell, or who blew up the amp while working that rare mult.
Score rumors archives - http://lists.contesting.com/_3830/
Post your contest score to the 3830 score rumors list - http://www.hornucopia.com/3830score/
K9JY's contest resources - http://k9jy.com/blog/k9jy-resources/
N8VW's Contest Blog: http://n8vw.radiosport.us
Radio sport Blogs / Another Calender http://radiosport.us
SKCC sprint http://www.skccgroup.com/sprint/sks/
Contesting Wiki http://www.contestingwiki.com
Also feel free to add any contest links (tips etc) to this thread. If they are useful I will put them in the first post.