Phil Torrone has put together a guide of open source hardware that was produced over the past year. This is sure to be a growing category in the next few years.

"Each year we do a guide to all open source hardware and this year there are over 125 unique projects/kits in 19 categories, up from about 60 in 2008, more than doubling the projects out there! – it’s incredible! Many are familiar with Arduino (shipping over 100,000 units, estimated) but there are many other projects just as exciting and filled with amazing communities – we think we’ve captured nearly all of them in this list. Some of these projects and kits are available from MAKE others from the makers themselves or other hardware manufacturers – but since it’s open source hardware you can make any of these yourself, start a business, everything is available, that’s the point."