Though not mountain bikes, Rivendell Bicycles is offering two new 650b wheeled bikes in 2009.
The Betty Foy is ladies mixte frame. Lugged, and Taiwanese produced.
Sam Hillborne is the traditional version.
This bike uses 650b wheels on sizes 48cm & 52cm.
To quote Rivendell on 650B,
"The wheels are 650B. Five years ago, were rare in the U.S., but no more. It's well-supported in this country--it's even trendy--and has a secure future."
Good work Grant.
Check out www.rivbike.com for additional info!