[tossaway9000]

NetBSD has an active port (though "active" for NetBSD is not as "active" as other projects, but it still builds and runs): http://wiki.netbsd.org/ports/sh3/

Aside from the Dreamcast, there's a few Japanese NAS devices that run the SH3 port too.

[tyingq]

Ah, okay...the Jornada is on their list too. http://wiki.netbsd.org/ports/hpcsh/hpcsh_support_status/