Games Workshop Errata: Your number 1 resource for many question. Not comprehensive, but these are the definite answers.
http://www.games-workshop.com/gws/content/...3000006&start=2Although Games Workshop states that their FAQs are not official, for the purpose of consistency, Games Workshop FAQs are considered official rules in rules discussion. Using different house rules is great, but has no place in discussing how rules should be played.
Direwolf FAQ: A good guide if your stuck on a rules question, but often they are not official responses (many are simply questions asked to a GW Development Team member, not officially released).
http://www.geocities.com/mi_whplayers/dwfaq.html