Hi! I just wanted to let you guys know that I've just launched a crowdfunding campaign to create the "Celeum Domain Server". It's a
quad-core@1.7ghz ARM chip with 2GB of RAM, running Ubuntu Server and a custom fork of Zentyal (because the official repos don't support ARM, and because some packages like zentyal-email won't currently compile on ARM Ubuntu). If you're looking for a drop in replacement for a Windows Domain Controller that's tiny, ARM based, has no moving parts, and is ready to just turn on and deploy - this is it.
Check out our crowdfunding campaign at
http://www.indiegogo.com/projects/celeum