Works in Scarlet Monastery, Dire Maul & Gnomeregan for sure.
It's cheap but easy, if you dant have a key but need in the dorr to one of these places take off all your gear with durability on it (no repair bills that way) then aggro a mob and get yourself up next to the locked door. Make sure to use low lvl spells/abilities to keep the mob well mad at you then die by the locked door. Release and run back to body walk through locked door in ghost form and rez by clicking Accept on rez now button. Wallah!!! On the other side now open door for party and re-equip your gear. BTW next time tho bring a key and save some time :P