If you are thinking of the s939 ver. of the 3400+, there are no good boards. It is a limited edition chip, made for an oem, that got into the general market. There are no common bios that support it. The best you could do, if you already have one, is get one of the gigabyte nforce3 ultra boards, and do a manual setup in bios.
On the other hand, if you are looking for s754, the asus K8N <A HREF="http://www.newegg.com/app/ViewProductDesc.asp?description=13-131-512&depa=0" target="_new">http://www.newegg.com/app/ViewProductDesc.asp?description=13-131-512&depa=0</A> is a great deal.