You can download the VMs needed to play these games several places; below are just two of the links:
PocketTADS -
http://www.progsoc.org/~drbatter/ptads/
Pocket Inform -
http://www.inform-fiction.org/zmachine/wince.html
The Inform VM alows you tho play all the old Infocom Games like HHGTTG, Zork and Planetfall, but developers have been making games for this platform as well as TADS for years now. In fact, the 2004 IF Competition just completed a month or so ago.
For more info on IF in general try
http://www.brasslantern.org/
As for games, best place to look is here:
http://www.wurb.com/if/