I found out from the Life of Andrew blog that there is a new source for Boost information available. It's a Creative Commons licensed book covering a wide range of Boost libraries, some of which are usually under-represented documentation-wise (looking at you, ASIO). It was originally written in German by Boris Schäling, but Andreas Masur has translated it into English for those of us who aren't so culturally adapted.

A brief skim of the book gives an extremely promising impression and I think it'll be one of the first resources I point newcomers to Boost to in the future.