http://www.freealloil.com/freealloil/freeall.html
http://www.crustyquinns.com/tech/easyout.html
http://www.asashop.org/autoinc/may2003/techtotech.cfm
if you can drill thru the center of the broken bolt with a bit aproximately 2/3 the dia of the broken bolt, untill the bit goes ALL the way thru then soak the $%^ out of it with FREEALL penetrating oil,(this stuffs amazing) this will allow the oil to soak in from both ends of the broken threaded section, let it soak at least 30 minute while you re-apply more spray oil every few minutes, then insert the easy out and gently twist the broken bolt remains out of the threaded hole, BTW heating and cooling the bolt, helps. heat with a propane torch the cooling it with the spray oil helps to lossen its grip on the threads if its really stuck