WorldGuard Spawn Point Flag adds a flag to WorldGuard: respawn-location. Players who die inside a region with this flag set have their respawn location changed.
This mod requires WorldGuard Custom Flags 1.6 and (of course) WorldGuard.
/region flag city respawn-location here
sets the respawn location of "city" to your current location.
/region flag city respawn-location 340,45,-230
sets the respawn location to x=340, y=45 and z=-230.
/region flag city respawn-location
resets the flag to its default value (nothing, the player will be respawned at his normal spawn point).
Some other useful WorldGuard Custom Flags plugins
If you have problems with this plugin read the F.A.Q.. If this did not help you, you can receive help here.