I use Rawr and maxdps to figure out which drops I can benefit from but it's a very tedious and manual process. Sometimes I join a raid without knowing whether I'm likely to get any drops that I need. Are there any tools which can help answer the question which raid instance I should focus on to improve my gear?
There's also Kaliban's Loot Lists that detail drop recommendations by instance/boss and class. You can (manually/mentally) compare against your character and figure out which bosses you particularly need.
Besides that, you can run character auditors like http://be.imba.hu/ and http://wow-heroes.com/. I like WoW Heroes for the character comparison option and Be Imba! for the raw auditing and instance suitability chart.
Wowhead has a great feature for searching for upgrades. You can plug in the lowest and highest item level you'd like, what classes it is for, and any other filters.
They also have a Stat Weighting section which helps you find upgrades by taking a SWAG at the right stats for your class/roll. You can also look for crafted-only items, specify which kind of gems you're using for the sorting, all kinds of stuff.
Here are some examples:
- Paladin (holy) weapon upgrades beyond 251.
- Druid (bear) wrist upgrades beyond 251.
- Death Knight (frost DPS) upgrades beyond 200.
It also shows you where items drop, right below the name of the item.
<Boss> - <Zone> <Raid Type>.
I know this question is old, but I'll answer with some current(Cataclysm 4.0.6) info incase anyone else finds this and is curious.
I use guildox.com and maxdps.com, filtered for the content my guild currently does. Once you plug in your realm and name you can see what gear you have and how much of an upgade everything is.
You then have to manually keep track of what drops where, or just use atlasloot and manually add everything to your wishlist.
At this point in the game(4.0.6), don't expect too many upgrades. I've gotten 0 loot so far, and only need 2 or 3 items per zone on normal. Rep rewards, Valor gear, and BoE craftables are really good now.
If you find your character on armory ( http://www.wowarmory.com/ ), there is a 'Find an upgrade' button next to each of your gear item. That should tell you where you can find better items to what you currently have and which bosses drop them.
You could use a website like AskMrRobot which loads your character details from the WoW armory and then calculates upgrade paths, item reforges, gemming, and enchanting for you.