I have never played Feral so it's hard for me to say with any certainty how you should approach gearing up one. I can give you a few tips, though.
1) You will do adequately in Rogue gear, except that to tank you should target leather items with a high Armor value. In pre-Heroics, there's precious little to choose from except the Clefthoof set (leatherworking). Fortunately, it's BoE. In the same vein, Strength is superior to AP in almost every case, but don't stress about it. To tank, gear for Armor, Stamina, Agility, and Strength, roughly in that order.
2) CE has the best pre-Kara feral staff. Keepers of Time has your head enchant. Aldor/Scryer have the shoulder enchant. Otherwise, consider getting enough rep with each faction to buy the blue PvP set. It's not bad at all for tanking.
3) If you don't have time to do Kara and/or Heroics for the precious few dedicated Feral drops, go the PvP route. Sure, you'll end up with far more Resilience than you'll ever use in PvE, but the gear is absolutely loaded with good tank stats. If you can handle badge grinding, though, you'll find the best PvE gear you can get from the badge vendor.
4) Your professions matter little, since there's no BoP stuff that will help you much if at all. Engineering has a nice helm (more DPS than tanking, but w/e). There's not much to pick from in crafted gear otherwise (aside from the aforementioned Clefthoof set). Alchemy gets you a nice tanking trinket, but you can't use items in Bear/Cat forms (until 3.x anyway).
5) Be prepared for disappointment as a Feral Druid in endgame. Sure, you tank some encounters really well, and you do okay damage, but your only real advantage is that you provide both a tank and a DPS in a single raid slot. However, if you stick it out to 3.x, there are some nice Feral changes coming down the pike that will make it fun to play again.