My personal favorite Doom port is GFDoom:
http://home.freeuk.com/gamefreaks/pql/gfDoom.htm
Download the Arm version. (XScale=StrongArm=Arm)
It is one of the more advanced ports, and lets you play in landscape mode. There is a thread I started on how to set it up to use the record button and jog dial in for fire and open (to make it more playable in landscape).
Thanks for the links to Hexen cherdman, that should be fun to play.