Cartographer is currently one of my favorite addons. I pretty much can't live without it in battlegrounds. From the download site: "Cartographer is a modular, lightweight, and efficient framework for manipulation of the world map". What that means is awesomeness. Here are my favorite features:
Foglight : Shows unexplored areas on the map. You can also set it to show you what areas you haven't yet uncovered.
Group Colors : turns all your party's and your raid's POIs into circles colored based on class, and shows a number on them based on their raid group.
Zone Info : on hovering over a zone, it will show the levels of the zone, the instances in the zone, their levels, and the number of men the instance is made for (e.g. 5-man, 40-man).
Look 'n' Feel : allows you to change the transparency, position, and scale of the world map.
You can download it at it's Curse.com page. And while you're at curse, register with the site and you can add the mod as a favorite. You can then check the favorites page to see when there's been updates to the mods you use (and can also redownload addons if you're installing on another computer or have wiped your mods).
