You probably all know what SCUMMMV is and what it does. My answer is usually use DOSBox but for the PDA that is different. For me PocketSCUMM is the only relailable way to play games like Monkey Island on my PDA. it still has some issues and does not have a qwerty keyboard or even a keyboard at all most of the time which is a pitty but it does work. Check it out.
http://arisme.free.fr/PocketScumm/index.php
If you want some games to play with it then there are some on abandonia that are supposed to be compatible (I haven't tried them yet). If you know more of them are please post it so we can add them to the list.
Beneath a Steel Sky
Flight of the Amazon Queen
Indiana Jones and the Last Crusade
The full compatibility list can be found here
http://scummvm.sourceforge.net/compatibility.php