I am a big fun of the Microsoft Gadgeteer (if you have not figure it out by now :) ). Right now there is pretty much only one company in the US that is actively developing Gadgeteer modules and boards - GHI Electronics. So I follow that company very closely. Today they put up another Gadgeteer related product - DuinoProto. It is not a Gadgeteer module (it doesn’t follow the standard), but rather a solution that should help prototyping modules much easier and also should bridge the gap between Gadgeteer and existing shields and modules for Arduino(s). There are other scenarios for using it as well.
As you can see it has an Arduino shield form factor. There is also a nice prototyping area and a place to put up to four Gadgeteer socket connectors. I am definitely going to try it as soon as I have more time and get my hands on one of these.
Oh, did I mention that you can get one for free (some conditions apply)?! Here you go!