I just received a new computer that this company is calling a "CoreCrib". It's a Apple G4 tower motherboard and powersupply in a lower cost case that you can add harddrive video optical drives and other parts yourself (the kit comes fully assembled)
http://www.2khappyware.com/corecrib.html
(They made mac news headlines a couple of weeks back about their desktop "Ibox" design)
I purchased a Dual 1.2Ghz kit. It looks like they have a new case option (link above) that offers <b>front</b> USB firewire and Audio OUT (wish I had waited) as the original case wasn't as good as that (older case had a plastic window and LED fan inside... fun but lower the build quality of the case slightly)
The prices start at $379.99 for a KIT without processor (friend picked that up along with a Gigadesigns 1000Mhz upgrade from Macsales.com).
Also looks like they have complete solutions now starting in the $700 range and their high end prices beat Apple's by a good margin.
They are new in the process of the business and selling them but had quick response time to questions. They had a initial firmware issue (the first kits had older firmware but they fixed that quickly and now seem to be on their way)
Not the best option if you are happy with Apple's low end systems (more so with Apples new $799 emac) but for around the price of that emac you get a slightly faster system that can be expanded on later.
My friend made a 1.0Ghz killer gaming system for under $800.