CDRip is a library that provides methods for extracting data from audio CDs. It is used by many popular CD ripping applications such as CDex or BonkEnc. The library provides a C API to allow it's use from different programming languages.
Easyfreedb is a cross-platform C++ library for accessing data on a freedb server. It supports protocol level 6 (UTF-8) and uses Boost's LL parser framework for parsing. Easyfreedb has a C-wrapper to make it easy to use from other programming languages.