Soundfont Librarian: This librarian is a tool to manage, edit, and customize SoundFont banks. You can load several banks each in their own Windows, then simply drag-and-drop presets from one bank into another, to custom create banks containing just the presets you want in an all new bank. Save your creation back to disk when finished.
SF2 Splitter: Simple tool that extracts instruments from SoundFont files.
rosegardenmusic - Music composition and editing environment based around a MIDI sequencer that features a rich understanding of music notation and includes basic support for digital audio.
libremusicproduction - Community-driven online resource, focused on promoting musical creation and composition using free and open source software.
sfzformat – The original rgc:audio sfz page at sfzformat.com maintained for posterity.
DevXchange – The Cakewalk sfz Format Page, with example downloads.