I've already mentioned a couple of Games Workshop forums (Warseer and Dakka Dakka) but it's high time I showed you another.
The Warhammer Forum is a British based, no nonsense forum covering all GW games but specializing in Warhammer Fantasy battle. It's tagline is does exactly what it says on the tin, which is a reference to the famous Ronseal TV adverts. It seems to have a high proportion of veteran and tournament gamers with a fairly strict bunch of moderators. This means that spelling, grammar and punctuation is better than average and that topics are debated thoroughly. Perhaps because of the British bias there is less preference for RAW and more tolerance of 'common sense' interpretations of rules and sportsmanship. Check out this thread on the WPS tournament rulespack for a perfect example.
Because it is hosted and populated by Brits it is excellent at keeping me informed on upcoming tournaments. I also use it's 40k boards to kick around ideas. The battle reports section is also particularly good, probably due to the aforementioned number of tournament players.