libgaudio is a C/C++ library to facilitate easy incorporation of sound and sound effects into games. Samples are loaded into memory and playback is then triggered or stopped. The system mixes any number of concurrently playing samples together (up to a predefined maximum). It is also possible to include a background MP3 soundfile in the mix.
liblcd is a simple Linux user-space driver for serial-interface LCD alphanumeric and graphical displays. It was written specifically for the Scott Electronics G12032 graphical display, but it should work with most any LCD that can understand ASCII. Even if your display is not a graphical one, you should be able to take advantage of the text functions.
mcal stands for Modular Calendar Access Library. libmcal is a C library for accessing calendars. It's written to be very modular, with pluggable drivers. One of the primary drivers it handles is ICAP, allowing access to remote calendar stores. libmcal is the calendar equivalent of the IMAP c-client library.