Not asking much eh? Gearing for Heroics is not often focused on, gearing for Kara is, so you'll have to tinker.

No resources that I know of pertaining to boxing.

Many resources for rating gear or choosing upgrades.

Wowinsider has consistent guides for gearing up for karazhan, which is a step above heroics, so the data is useful.

Stealthy has a guide around somewhere on this site about gearing up a shaman in outland, but I believe that's primarily elemental.

http://elitistjerks.com/f31/ Major resource, there are threads for most builds there with all kinds of data. There is also threads about leveling specs and tricks in their public forum.
wow-loot.com
tankadin.com
shadowpriest.com (specifically the stickies in http://shadowpriest.com/viewforum.ph...e61c31eecf50a3)

One of the best simulations out there for gear and enchanting and gemming is Rawr. It's available at a link on the elitistjerks forum devoted to RAWR.

It started as a feral gear simulator but it now has very useful modeling sims for at least 10 common builds, allowing you to target the best outfit among gear you have and also figure out what upgrades will give you the most impact. Rawr is a monster but it takes patience to work with.

maxdps.com
lootrank.com

Some utility, but some questionable.
http://gear-wishlist.appspot.com/


Tons of stuff there to wade through.