All of these documents (in fact, this entire homepage set) are bundled with the library source, under the docs subdirectory, for releases and snapshots. The sole exception is the automatically-generated source documentation, available separately.
In addition to the distribution documentation (these pages), we also have a set of HTML documents generated from the sources themselves, using the Doxygen tool. These are useful for examining the signatures of public member functions for the library classes, etc.
The latest collection is for the GCC 3.0 release, libstdc++-doxygen-3.0.tar.gz (3.8MB), viewable online. The collection is also available in the libstdc++ snapshots directory at <URL:ftp://gcc.gnu.org/pub/gcc/libstdc++/>. You will almost certainly need to use one of the mirror sites to download the tarball. After unpacking, simply load libstdc++-doxygen-3.0/index.html in a browser. Feedback (and additional documentation!) is welcome.
This is a short list of text files pertaining to this implementation of ISO 14882. A brief description follows the name of the file.