Boost 1.67 is now available:

Boost Version 1.67.0

There are two new libraries:

• Contract: Contract programming for C++. All contract programming features are supported: Subcontracting, class invariants, postconditions (with old and return values), preconditions, customizable actions on assertion failure (e.g., terminate or throw), optional compilation and checking of assertions, etc, from Lorenzo Caminiti.
• HOF: Higher-order functions for C++, from Paul Fultz II.

Also, many updated libraries have been updated. See the announcement for details.