We all need reputation, in WoW for Heroic Dungeon keys, reputation rewards, cool mounts, etc.
To see where you are, and what to do next, look here:
WoW Reputation Calculator
If you want more detailed information, click on the links under spesific faction.
or if you want more, look no further than WoWWiki for the best resources on how to get high reputation (the fastest, easiest, etc): WoWWiki Reputation
EDIT: I just found a post in WoW EU Forums about this: WoWJuju RepCalculator. Same thing as the WoW Reputation Calculator, but with a bit more extended interface.
