In an attempt to consolidate the stickies, I'm creating this one central post with links to the pertinent posts. Keep checking back, as other links may be added as needed.
[Official] Map Editor DLC Community Wishlist
Dedicated Server Listings
Far Cry Community Websites
Official Xbox Magazine map picks
Ubisoft announces "The Official Far Cry 2 Map Editing Guide"
FilePlanet map pack
Comprehensive Ubi recommended maps list
Map editor tips & tricks:
Snapping objects that don't snap: by CrazyUncleDave
Starting a map: from fcmaps.net
Destructibility: by Agent00Kevin
How to make working elevators: by Map builder