Since I wrote my "IP04 and Me" blog post, I've made remarkable progress. My home phones now run completely under the control of the IP04, and I have that virtual receptionist I've been working towards.
A couple of weeks ago, I bought myself a Pogoplug (V2, gray) to try out. The PogoPlug comes with an embedded linux system, and is set up to externalize (through my.pogoplug.com) any USB storage device you connect to it. I wasn't as much interested in the services of my.pogoplug.com as I was in using the device as a general-purpose linux system.
My adventures with the IP04 have temporarily stalled as I start to think of how I want to use it in my home. I started off playing with the extensions, and quickly bogged down as I looked at all the various options I had. So, I'm taking a break and looking at this from a different angle.