Armadillo is a high quality linear algebra library (matrix maths) for the C++ language, aiming towards a good balance between speed and ease of use
Provides high-level syntax (API) deliberately similar to Matlab
Useful for algorithm development directly in C++, or quick conversion of research...
SQLiteC++ (SQLiteCpp) is a smart and easy to use C++ SQLite3 wrapper.
See SQLiteC++ website http://srombauts.github.com/SQLiteCpp on GitHub.
SQLiteC++ offers an encapsulation arround the native C APIs of SQLite, with a few intuitive and well documented C++ class.