OK, this is not specifically java related but I thought given past interest in parallelism and concurrency there might be some interest on the list.
The Parallella project has similar aims to the RaspberryPI, but with a focus on parallel computing - the aim to get a board out there with low power requirements and cheap enough for ordinary developers to experiment with parallel computing. The first boards will have 16 RISC cores (plus a dual core ARM processor) and they are aiming to have 64 core boards available next year if they reach their funding goals. The first 16-core boards should cost $99
An article on The Register gives some more background to the project: http://www.theregister.co.uk/2012/10/07/adapteva_epiphany_parallel_computing_kickstarter/print.html
Although the project is called "A Supercomputer For Everyone" it's clearly not a supercomputer by any modern definition.
I've no connection to the project other than that I signed up as a backer on kickstarter.