The programs that folks have put together for this thing are just.. silly. The serial connector on the bottom is meant to attach to a desktop PC to synchronize the address book, phone numbers, etc. Someone has written a VT100 terminal for it, and someone else uses it to capture datapoints from a GPS receiver. They've got cellphone-modem interfaces. There is an Infocom interpreter for the Pilot. There is a music synthesizer written by a guy I knew in Japan (hi Eric!). And the new versions have a complete IP stack in them, which can run over PPP over the serial interface.
This page is where I'm going to put my Pilot apps (once I've gotten around to writing them). It's also where I'll put links to Pilot sites that I find useful. I'll probably assemble RPMs of pilot development tools.. this is where you'll find the downloads.