Library/Software Engineering/Concepts worth knowing

This is a somewhat arbitrary, work-in-progress list of classes, libraries, and concepts that, IMHO, are "worth knowing". It's the kind of list where if I asked someone, "Tell me when it'd be advantageous to use ____ as well as some of the drawbacks to it," and they had solid answers for all the below, then I'd be very eager to work with them.


 * std::vector<>
 * std::deque<>
 * std::map<>
 * std::shared_ptr<>
 * std::weak_ptr<>


 * boost::any
 * boost::format

Should be, but aren't...

 * boost::constants - seems like this would be more useful if it contained more constants