WoW Census

The WoW census shows the total number of players in each faction, per each race, and per each class who self-report via the CensusPlus AddOn, which scans players around the mod's player character. The Census only includes characters that are level 10 or higher and that have been active within the past 30 days.

World of Warcraft Census

 * As of 10th, June, 2010 from WarcraftRealms.com:

Factions
Alliance Players 3,093,322 - 51%

Horde Players 2,921,524 - 49%

Total: 6,014,846