Abit, Tyan, Asus, MSI, Epox, all make dual cpu boards. Currently Celeron II's are not smp capable. fc-pga PIII's are smp capable if they have the cB0 stepping. As as I know all slot PIII's are smp capable. I'm currently building a dual slot PIII system using the Tyan Tiger 100 motherboard and 2 PIII 550E's. Check out this site for more info on dual cpus:
http://www.2cpu.com HTH and lemme know if you have more q's.