Autodoc Hotlist

Looks like the best bet. Works with perl so can be compiled for win32.
The Automatic Documentation System [Unix]
Mainly for C. A lot of manual work involved. Some C++ support, but no object hierarchy.
Bumble Bee Software [Win32]
C++, integrated with VC5, commercial, looks like it doesn't do automatic object hierarchy. Hard to tell from the docs they have on-line.
C++, written in Perl. Looks like templates have to be written in perl though.