The abundance C++ standard library implementations is quite surprising. You have at least the following:
- Apache's STDCXX (former RougeWave)
- STLPort -I used it myself in a couple of projects, and it is bundled with Borland C++ Builder
- SGI - well, this is mainly STL
- GCC's implementation
- Dinkumware - used in Microsoft's Visual C++
- ...and more
It is really astonishing - imagine all those people sitting and coding the standard library time after time, for years. You must be very devoted C++ programmer in order to participate in such a project.