MNMLSTC Core is a small and easy to use C++11 library that adds a functionality set that will be available in C++14 and later, as well as some useful additions, or some proposals that have not been completely approved yet.
If you're somehow stuck with gcc 4.8 and have to way to upgrade to gcc 5x series, mnmlstc's core implementation will boost your productivity in many ways. It has been in use here especially due it's implementation of string_view, variant, and it's collection of smart-pointers, especially observer_ptr. However, the list of things is surprisingly long, and you can find many useful patterns and classes here.
Besides of very clear programming style, you get a nice, searchable documentation plus example sections on the github page.