At the end of every year Makezine publishes a list of most interesting opensource hardware projects. And here is the list for 2010. Descriptions are a bit terse this time around but there were several new discoveries even for me even though I follow progress in open source HW all year round.
For me the most interesting projects from that list are Freakduino-Chibi, An Arduino-based Board For Wireless Sensor Networking and the Bus Pirate.

Hopefully I can use Freakduino to replace Arduino + XBee combo that I currently use to communicate with greenhouse and the Bus Pirate looks just interesting and might be helpful sometimes. Pandaboard is missing from that list for some reason, probably because it was released so close to the end of 2010 and is already backordered well into 2011.