kPlaylist is a multi-lingual Web-based music streaming system. It can be used as a private or public jukebox. It uses MySQL as database, reads files as MP3, Ogg, WMA, and others and includes a user signup tool, search engine, user editor, personal options, personal and shared playlists, listings of new and popular music, a randomizing feature, and a quick way of browsing albums. Upgrading and installation is automatic.
dc_qt is a Direct Connect client based on DC++. The GUI is based on Qt. The goal of the project is to provide features not seen in other clients, while providing the easiest user interface possible at the same time. One interesting feature is the ability to run the client and the GUI on different machines.
Mutella supports all the functionality required to participate as a full-featured node in the Gnutella network (which implies support for file search, download, and sharing). It is optimized for a high-bandwidth connection where it sets standards for the server performance and stability, but it can also run on a modest-speed line. It features real multiple search support, passive search (all query-reply packets are checked against local search list), automatic re-submission of the queries, unlimited download retry, automatic search for alternative locations when download fails to start immediately, auto-get function for broken downloads, and much more.
Soulseek (http://www.slsknet.org) is a communication and file-sharing system. It is quite similar to Napster: it lets you exchange files, search for files, chat with other users in public and in private, browse their files, and get recommendations for music. SoulSeek for Linux is a GUI client for the system written in Python/wxPython. It includes all the major functionality: chat, searches, and file transfers.