I think your two best bets for finding C++ code are to go to the popuplar open source repositories.
- CodePlex: http://codeplex.com
- Google Code: http://code.google.com
- SourceForge: http://sourceforge.net/
These all have high quality C++ projects you can take a look at. I don't think there's a great metric for judging quality on a large scale. I would start with the more popular projects which may be more likely to have quality code.
