I use the Great Planes wooden building board. It is 16x48x3/4. It is balsa glued up like a butcher block. Pins go in easy and hold tight. It's expensive ($30) but it works well for me. Here's a link:
http://www2.towerhobbies.com/cgi-bin...?&I=LXPF36&P=0
They offer smaller sizes.