I got Asterisk and Asterisk-Gui running on the plugpc. I used apt-get to do most of this. I looked into getting freepbx onto the plug but I was missing kernel-headers and couldn't find them anywhere for the arm architecture.
Since the two choices looked like learn asterisk-gui (which is not nearly as nice as free-pbx) or mess around with compiling kernels, I went with the new gui, I think it will also require a lot less resources than free pbx.
Additionally I'm using ubuntu 9.04 installed on an SD card from the sheeva plug installer, not the install I got when it came as this seemed to have a few issues. installer is here:http://plugcomputer.org/index.php/us/resources/downloads?func=select&id=5
Once this is installed, I only needed apt-get install asterisk to get that installed.
The gui was a bit of a pain since I couldn't get svn on the plug, so I used another machine with svn to download the latest gui from http://svn.digium.com/svn/asterisk-gui/branches/2.0/
then followed instructions found on google.
last error I ran into was that the location ubuntu store the web pages and where asterisk is looking for them didn't match up, so I did the following:
rm -rf static-http/
ln -s /var/lib/asterisk/static-http/ /usr/share/asterisk/
chown –R asterisk:asterisk /var/lib/asterisk
If you're used to free-pbx, the asterisk-gui does things in quite a different way, I'll be using this for the plug only, freepbx is a lot better, so if you do get that working please let me know how you did it