It is just a simple plugin that enables you to ride or force other player/mob to ride on top of you. Someone ask me to give this out so here it is :/
Should support any version, tested with 1.5-1.8
/ride: after executing this command, right click someone or somemob to ride him/it.
/rideme: after executing this command, right click someone or somemob to let him ride you.
rideme.ride: allows a player to ride someone
rideme.rideme: allows a player to force others to ride him.
You may punch player/mob off your head while you are ridden.
Note that it is possible to allow player to move mobs around with /rideme, it is not recommended to give any player this permission.
In Minecraft 1.7 and below, there is a visual glitch that make players see other player on top of them higher than it is supposed to be. In Minecraft 1.8 or above the position was fixed but difficult for player to see their way while something is on their head.