According to total number of servers monitored by GameTracker.com, these are currently the most popular versions running on Minecraft Servers:
#1 (34%) Minecraft 1.7.2 - View the List
#2 (15%) Minecraft 1.6.4 - View the List
#3 (12%) Minecraft 1.7.4 - View the List
#4 (12%) Minecraft 1.5.2 - View the List
The new Minecraft version 1.7.4 is quickly being adopted by server admins. If the current trend continues, it should take over the #1 spot within a month's time!
To browse all available versions, visit our Minecraft homepage: