Mixxx is software for DJs that provides everything needed to create live mixes. It allows you to beatmatch songs and crossfade them together, like you would with turntables and a mixer. It runs without any extra hardware, and offers a wide range of advanced features including comprehensive MIDI controller and vinyl control support. To obtain the lowest latency and highest responsiveness, it uses hardware video acceleration and takes advantage of multi-core CPUs.
Neformal is a small audio player with a file manager and the ability to play file by file. It can keep bookmarks for favorite directories. It can compute RMS statistics for 16 bit PCM WAVs. Song lyrics are supported (via lyricwiki.org). Drag and drop can be used to interact with other applications. ID3v1 and ID3v2 tags are handled flexibly. The charset for tags can be selected. There is a built-in viewer for images and text files. The output device can be selected.