Thanks to a comment on my previous open phone post, I am reminded that I forgot to mention OpenMoko. This is a neat looking touch screen Linux phone that should be available in February 2007. I haven't seen one yet, although I have played with the Greenphone and I know someone who has ordered and received a Greenphone, so they are ahead by a couple of months.
In the homebrew mobile club, we are talking about making something with a physically bigger (perhaps 3.7" VGA) touch screen than the OpenMoko (2.8" VGA) or Greenphone (smaller QVGA), big enough to show a more usable keyboard. The existence of multiple open phone projects is great, since the nature of the open source community is that we can all share and reuse code for device drivers, user interface components and applications. We aren't building from scratch every time we want a new feature. In the meantime several of us will have Greenphone's, OpenMoko's and TuxPhone's to play with.
The big screen is pretty much the most expensive part. I like the concept of building a phone, keeping the screen and CPU for a long time, but do upgrades like replacing the GSM modem with a 3G one by performing electronic surgery inside the case.