Legion PvP Guides I use a Google Alert to send me new potential links on a daily basis.
Arena Junkies class discussion: good information and jackwagons.
PvP Leaderboard: See which talents, glyphs, stats, and gear top WoW PvPers are selecting.
ArenaMate: A good way to track the current rating needed for the various titles (e.g. Challenger) in arena and RBGs. Also has the current ladder of top rated players.