Software
SonicStage
Sony's official NetMD software, for Windows
Installation on modern PCs requires a guide [coming soon]
Download: From Optical Garbage [will host ourselves shortly]
linux-minidisc
A reverse-engineered, cross-platform tool for NetMD devices. Allows full quality SP transfer over USB, unlike SonicStage.
Original release: https://github.com/glaubitz/linux-minidisc
Vuori fork: https://github.com/vuori/linux-minidisc
Platinum-MD
A cross-platform frontend to Vuori's linux-minidisc tool. Easier to use than the command line original tools, especially on Windows.
Github: https://github.com/gavinbenda/platinum-md
Reddit post: https://www.reddit.com/r/minidisc/comments/cxg9hv/netmd_app_full_sp_quality/
Multi-platform update: https://www.reddit.com/r/minidisc/comments/fqmn00/platinummd_now_available_for_mac_windows_and/