Here is a list of all documented namespaces with brief descriptions:
[detail level 123]
| ▼N__gnu_cxx | GNU extensions for public use | 
| N__detail | Implementation details not part of the namespace __gnu_cxx interface | 
| Ntypelist | GNU typelist extensions for public compile-time use | 
| N__gnu_debug | GNU debug classes for public use | 
| N__gnu_internal | GNU implemenation details, not for public use or export. Used only when anonymous namespaces cannot be substituted | 
| N__gnu_parallel | GNU parallel code for public use | 
| N__gnu_pbds | GNU extensions for policy-based data structures for public use | 
| N__gnu_profile | GNU profile code for public use | 
| N__gnu_sequential | GNU sequential classes for public use | 
| Nabi | The cross-vendor C++ Application Binary Interface. A namespace alias to __cxxabiv1, but user programs should use the alias 'abi' | 
| ▼Nstd | ISO C++ entities toplevel namespace is std | 
| N__debug | GNU debug code, replaces standard behavior with debug behavior | 
| N__detail | Implementation details not part of the namespace std interface | 
| N__parallel | GNU parallel code, replaces standard behavior with parallel behavior | 
| N__profile | GNU profile code, replaces standard behavior with profile behavior | 
| Nregex_constants | ISO C++-0x entities sub namespace for regex | 
| Nrel_ops | The generated relational operators are sequestered here | 
| ▼Ntr1 | ISO C++ TR1 entities toplevel namespace is std::tr1 | 
| N__detail | Implementation details not part of the namespace std::tr1 interface | 
| ▼Ntr2 | ISO C++ TR2 entities toplevel namespace is std::tr2 | 
| N__detail | Implementation details not part of the namespace std::tr2 interface |