ClassBuilder is freeware CASE tool targeted at the C++ developer, running on Win2K/XP/Vista/7. It lets you create, manipulate and navigate classes, class relations, class members and class methods at a high level of abstraction through a graphical user interface
Implements only class and sequence diagrams, but this is often enough to write good-quality code and document your work. Has a robust code generation feature and a good template-based document generation. No round-trip, but reverse-engineering is available.