There's a long thread on this already (even titled almost identically):

Show Us Your 650B Conversions

That said, this gives me another excuse to show two of mine.

Early 1980s Shogun 1500 tourer converted from 27" to 650B with relocated cantilever bosses and other frame mods:



It's undergone a lot of component changes since its initial build shown above, and has happily traversed almost 1000 miles of dirt roads and trails and has climbed remote mountain passes with aplomb:





And my wife's Soma Buena Vista mixte, which I bought new for her and built up as a 650B townie/errand bike: