Florida based Psystar announced an Apple Mac Clone for $399.99, but their site is already down. The reason for that could be high traffic, but it also could be that Apple already moved against them. As you know there are no Mac clones on the market. Apple does not like the idea that the Windows world has embraced.

Update:
More details on the Psystar Open Computer

The specification of the Mac Clone would be including 2.2GHz Intel Core 2 Duo CPU, 250GB HDD, and 2GB RAM.
The OpenMac would come with Leopard pre-installed. There are of course EULA issues with that.
In any case I do not see there being any Mac Clones anytime soon.
More details on Arstechnica and MacRumors and maybe on the Psystar site if its up again.