just do like vladimirjp told - put both scripts - the MJPolyTools and the MJPolyToolsUI into your scripts directory, update your userSetup.mel (type -> MJPolyTools;) which is also in your...

try selecting an edge and hit "Edge Loop Split". this would be the most used function from MJPolyTools I guess.

another script I use constantly for modeling is SpinFaces.mel
you can find it at...