I just read on the news page that David Querbach has gotten funding for 
an embedded-ppc port of NetBSD from Real-Time Systems Inc.  

Possibly others will become involved in the port eventually.  This product 
contains an embedded-ppc cpu, and costs only $300:

  http://www.amazon.com/exec/obidos/ASIN/B00004XONG/

It might make a useful development platform if evaluation boards cost 
too much.