It shocks me that I can't find a site where there are tons of custom zombie maps WITH a ratings system. I must've been spoiled with a site like New Vegas Nexus, which had a vast library of mods with a good ratings system and thousands of active contributors. I just downloaded a pack of zombie maps off of fileplanet (with no ranking system) and am ranking them all as I play them to keep track of ones I should and shouldn't play again.