Libev is a high-performance event loop for C (with optional and separate interfaces for C++ and Perl), featuring support for I/O, timers (relative and absolute, cron-like ones), signals, process status changes, and other types of events. It has both a fast native API and libevent emulation to support programs written using the libevent API. Differences to libevent include higher speed, simpler design, more features, less memory usage, embedability, and no arbitrary limits. libev supports epoll, kqueue, Solaris event ports, poll, and select.
Device::ParallelPort is a Perl API that allows low level access to the parallel port of most computers. It does this by using a number of drivers, which can be customized and added to, including Linux (direct and parport), Win32, Script, Dummy, and more. It also contains a number of direct access devices including an example printer and a relay controller card.
The TunePimp library is an audio file tagging library that uses MusicBrainz for track identification/lookup. It will attempt to automatically identify the files, and will present the user with possible matches for files that are not automatically identified. Once the files are identified, it writes new metadata tags to the music files and writes the files to a user-defined directory hierarchy. It supports WAV, MP3, Ogg Vorbis, and FLAC files.