The new Durons (FSB 266MHz) are just toned down versions of the Athlon XP Thoroughbreds - I think with a smaller L2 cache. The 1.6GHz and 1.8GHz Durons are made from the XP 1900+ and 2200+.
Motherboards which support those Athlon XPs can run these Durons - although the boards may not be able to detect the correct settings - you may have to do it manually.
Usually BIOS updates will add support to new CPUs. Check for BIOS updates for whichever motherboard you choose.