Been awhile since I played my feral but he was Mr. Fuzzybuns specced.
As a feral tank you want as much Stam and Agil as possible, while trying to get your defense to 540 cap (@ lvl 80) as fast as possible. You want lots and lots of Dodge too (remembering that Parry and Block are useless). Armor is always nice, though not quite as important as pre-WotLK.
I never specced cat, but you would want hit and crit instead of defense, while keeping stam and agil. Mostly the difference is in talents as mentioned.
wowwiki.com usually has some good builds and write-ups, worth checking out.
