The Boost Interfaces Library (BIL) by Jonathan Turkanis has been officially announced on the Boost mailing lists. The library has it's home page at http://www.kangaroologic.com/interfaces.

In brief the library allows you to define efficient run-time polymorphic references to non-polymorphic classes (i.e. classes without virtual functions). Jonathan does an excellent job of explaining the library in his documentation.

Discussion of the library it is occuring on the Boost Users Mailing list, which is accessible through GMANE.org.

I had some influence in the design of the library, so if you have questions or comments you can also post them here.