The Boost.Threads Library (C++ –> C++0x?)
Threads in C++ has been a long topic of pain and moaning, mainly because the C++ standard does not provide (until recently, at least) a platform independent and efficient support for threads built-in the language (POSIX pthreads lib is not C++; being a C library, it requires some careful use when dealing with multithreaded C++ objects which usually include constructors and destructors).
Boost is a set of free peer-reviewed portable C++ libraries (more info here and here) that implements for some time now the Boost.Threads library, which is a highly optimized (and growingly flexible) platform independent thread library (i.e. should work in Linux, OSX, Windows, etc), and that seems to be the candidate best positioned to be included into the next C++ standard revision (i.e. C++0x). When that happens, the need for 3rd party libs in C++ for platform independent thread support will be finally over.
You can learn a bit more about how Boost.Threads will handle threads in the following articles: