My CT has the opportunity to start putting together a house sound system.  What is the best type/size mixing board to put in?  We do mostly musicals with a pit orchestra, running multiple wireless bodymics and mics for the pit, but also use the theater for folk/rock bands between shows.

There are really so many aspects to this question its difficult to answer without more information about your needs.  I am assuming you want to stay in the analog realm.  Though I personally use a much larger number of inputs due to the scale of the shows I mix, I would imagine that you would want a 32 channel board.  This should be able to accommodate many musicals, as well as most concerts.  In terms of brands, a Midas console would be fitting in this situation (and they certainly are some of the best), but they tend to be pricey.  Despite their known power supply issues, the A-H GL series are also good boards at a lower price, and with a redundant power supply you should be fine.