This Script is inspired by the Houdini9,(the effect in the middle of mov following the links:
http://download.sidefx.com/images/stories/tutorials/95_fluids/jefflait_fluidstechevening.mov)
Now you can do that in Maya.
Usage:
a) Put this script in to

[C:Documents and Settings_USER-NAME_My Documents_maya_XXXX_scripts],

source it.

b)First selecet the cutPlane(planeStyle obj,but you also can use other poly obj,certainly ),
next select the obj you wantto separate,than type "yd_crackut:'" in the command line,
excute. oops,somebody is cracked :)

The following is cracKut by a planeStyle object.



The following is cracKut by other polygon object(like a poly sphere).



ps. The script is tested under winXP and Maya2008,
but I think it could works under the other env & version of Maya.