libkarma is a C library for managing the Rio Karma via TCP/IP. It supports all basic protocol commands and some advanced functions on top of these, like caching of the Rio database. There are two proof-of-concept tools included, riocp and chprop. riocp can be used to upload files to the Karma.
zlplay is an MP3 player that uses the zlcatalog system to organize songs. zlcatalog is a library for organizing things in non-hierarchical ways. Songs in zlplay can belong to multiple groups. Navigation through the groups shows songs and related groups. So, for example, it's very easy to start listening to all of your songs randomly and then when you hear a song by a particular artist, a single click switches the song list to songs by that artist.
The riofill utility randomly selects a list of MP3 files from a given directory and ensures they will all fit into the memory of a Diamond Rio portable MP3 player. Switches allow differently-sized Rios to be filled. By default, riofill uploads the playlist produced to a Rio player connected to the computer's parallel port using the Snowblind Alliance (SBA) Rio utility. Optionally, the generated playlist may be printed to stdout or saved in a file instead of being uploaded to the Rio.