Bukkit

11/01/11 Version 1.1
     - Made it so that server admins can edit allowedMaterials.txt to add block exceptions.

10/29/11 Version 1.0
     - NoJumpBuild is up for download.

It is possible to jump build if the player is sneaking, holds down jump, and continuously tries to place a block.  If the player clicks fast enough, a block will eventually get placed.  However, they will be penalized for each attempt since they will be unable to get the failed-placed blocks back.