id3j is a lightweight and easy-to-use library to create and add ID3 metadata tags to MP3 files. It only concerns itself with ID3 version 3.2.0 and only handles the most common types of information, but creating a tag and adding it to a file is much easier than with many other solutions. It also has one fairly esoteric feature that is interesting from a algorithmical standpoint, which is the ability to create CRC32 neutral ID3 tags. That means that you can add such a tag to any MP3 file and the CRC32 sum of the resulting MP3 file with the tag will be the same as the file without the tag.
Peyote is an audio player with a friendly MC-like interface. It is designed specifically to work easily with cue sheets. It plays wv (wavepack), WAV, FLAC, APE, Ogg, WMA, and MP3 formats. It supports ID3v2, APEv2, FLAC, and Vorbis tags; multiple playlists; and tabs. It can copy, move, remove, and rename files.
Goggles Music Manager is a music collection manager and player that automatically categorizes Ogg Vorbis, FLAC, MP3, MP4, ASF, and Musepack files based on genre, artist, album, and song. It supports gapless playback, features easy tag editing, and allows scrobbling tracks to last-fm.
DR14 T.meter is a commandline tool for computing the Dynamic Range of your music according to the procedure used in the offline meter released by the Pleasurize Music Foundation. It is very useful to measure how loud your music is and to understand that a good quality album always has a good dynamic. It's also useful for understanding the effects of the so-called loudness war.
Airtime lets you take total control of your radio station via the Web with intelligent archive management, powerful search, an easy playlist builder, a simple scheduling calendar, and rock-solid automated playout. Features include fades, cues, playlists, a programme calendar, Icecast, Shoutcast, and Soundcloud integration, DJ and station manager roles, JQuery widgets, Liquidsoap playout, and a record and rebroadcast functionality. Powerful media archive features 'watch' folders to allow stations to magically synchronize files, auto-import files, and has multiple directory support. Users can interact with it through any Web browser. It comes with an 'easy install' package.
audiopreview is a command-line tool that plays previews of many audio file types (Ogg, MP3, etc.), video file types (AVI, MPEG, Real, etc.), and Internet streams. It can also be used as a regular command-line media file player (i.e. play the files entirely like yauap or mpc123 would).