I have heard a number of people having the same problems, and have found it is usually caused by the magsafe charger not being properly grounded. Usually because the charger is a poor 3rd party replacement that causes problems when being connected, or to do with using the wrong generation of charger. (if you have a 13" macbook pro, you need a 60W magsafe charger, and 15/17" require 85W chargers)
If you use the original white tipped magsafe with a unibody aluminium macbook pro, you may have intermittent trackpad and isight issues (or any devices that are connected via USB), but if you touch the palm rest, it usually stops... as you are grounding the machine.
If these are the symptoms you are seeing, replace the charger with an apple original, but make sure its the range that was previously shipped with your machine (there is a white tipped one for earlier generations, then an aluminium right angled version for later unibody machines)
I hope this helps.