Linux-powered mobile phones

Neo1973 with OpenMoko $300 - $450
Greephone from Trolltech $695 USD (Sold out)
As of Apr 7, 2008 devices in both stores were "sold out" and Greenphone line is permanently closed with suggestion to purchase Neo1973.

Palm is developing Linux-based OS for Treos and Google pushing Android Linux-based mobile application framework conceptually similar to OpenMoko.

References:
Second open Linux phone goes on sale
Palm touts stability of Linux-based Treos