Bukkit

 ♦ Version 1.0
    Info:
        Contains every item I could think of that can be crafted into a block.
        Every item can be toggled with true/false via config file.
        Message sent when the command is run is configurable as well.

Sound, if set to true, will play when the player types /block, whether or not they have any items to compress. The message performs similarly. If set to false, neither have any problems.

If you are changing 64 diamonds (or other similar material) into blocks, there is one diamond left over. If your inventory is full, and there is nowhere for the diamond blocks to go, then the diamonds will still disappear, but the blocks will not be added to your inventory. This is being worked on full-force.