www.mwave.com sells some of the shuttle motherboards by themselves, however i only see the FS40 and FV25.
The FS40 is an athlon SIS 740 chipset which I believe will support upto athlon 2600+..
The FV25 is a socket 370 VIA PLE133T chipset motherboard that will support C3 upto 900mHz (problems with 1gHz and up)or Tualatin pIII upto 1.4gHz, should support all socket 370 Celerons to my knowledge.
several companies are coming out with mini-itx mobo's so keep on the lookput for systems from Iwill and MSI as well as VIA and shuttle.