I've tried to standardize mainly on Linhof and Sinar-sized boards, using an adapter board for Linhof boards on my cameras that take Sinar. Lenses that don't fit on a Linhof board are mounted on the larger Sinar boards. I've also got some lenses on Linhof 23 boards that I use with the Linhof Wideangle Focusing Device on the 4x5" camera or with a Linhof 23/45 adapter for longer lenses.
The exceptions are the Korona 7x17" camera, which I'll convert to Sinar at some point, as I did my 11x14" American Optical, and the 5x7" Press Graflex, which can't use such a wide variety of lenses anyway, but I've been thinking of making an adapter for Linhof boards on that one as well.