I am so excited to see how many people have joined various groups in the last year! Last April I compiled a list of the best LinkedIn groups for printed circuit board professionals and enthusiasts.  Many changes have occurred since then, with the addition of new groups and the demise of others.  Below is my take on the best groups for 2010.  I also want to point out a few groups I find to be great concepts, but which have yet to find the type of traffic necessary to sustain …