The Boost Exception library supports transporting of arbitrary data in exception objects, and transporting of exceptions between threads.
In C++, writing a loop that iterates over a sequence is tedious. We can either use iterators, which requires a considerable amount of boiler-plate, or we can use the std::for_each() algorithm and move our loop body into a predicate, which requires no less boiler-plate and forces us to move our logic far from where it will be used. In contrast, some other languages, like Perl, provide a dedicated "foreach" construct that automates this process. BOOST_FOREACH is just such a construct for C++. It iterates over sequences for us, freeing us from having to deal directly with iterators or write predicates.
Portable move semantics for C++03 and C++11 compilers.
Boost.Parameter Library - Write functions that accept arguments by name.
Execute arbitrary code at scope exit.
A common infrastructure for throwing exceptions from Boost libraries.
Runtime/Compile time copyable type info.
Typeof operator emulation.