First, I agree with Jeff -- a text viewer capable of handling larger files like the Etexts is a must.
How about a expense report application (or does Quicken handle that adequately)? I'm currently beta testing an expense report application for a different platform, and it is the best expense reporting program I've ever used. (I'll post details about it when the beta is concluded... which should be soon since the beta has proven to be very stable so far.)
How about a macro application to help automate repetitive operations?
Just my guesses (don't have a Zoomer yet).
CragSubj: Suggested applications