Spawning Players Randomly

I need to spawn players at random locations within an arena filled with buildings and houses (basically it's a town and yes, there will be different arenas). I want to spawn them so that no player will be spawned within a 20 block radius of another player. How would I do this while making sure that players are not spawned on top of buildings or anywhere other than the ground?

 

Try Random Spawn, there is a command to set the random spawning area.

http://dev.bukkit.org/bukkit-plugins/random-spawn/

 

Enrux
Thanks for the reply but that isn't quite what I'm aiming to do. I need to actually determine which locations are valid (not stuck inside a building or not on top of a building) which I don't think RandomSpawn does.

 

Mmm, this is quite a bit of logic, basically you should go about it like this

loop:
random number between the corners
if it is in 20 blocks on a player, repeat
if the block above it isn't air, repeat

how you translate that to code, is your job dude .