If you are using Linux check out CCRMA. They are developing and distributing tons of stuff (in a project called Planet CCRMA).
Also check out the programs developed by NOTAM.
Ardour - Linux and OSX freeware multi-track editor – a UNIX-version of protools.
Audacity - cross-platform open source multi-track sound editor
IXI - somewhere in between real-time processing and soundtoys
Max/MSP - commercial graphical "programming"
Pure data (or Pd) – cross-platform open source modular program similar to Max/MSP
Pure data libraries:
- Gem - GEM (Graphical Environment for Mulitmedia) is a library for working with real-time 3D graphics
- Pmpd - excellent library for physical modelling
Soundhack - Tom Erbe’s classic FFT based sound-editor (OSX)
Here is a list of software tools for translating images to sound (and sometimes vice versa)
Bitmap Player (windows)
Spear: analyses sound to sinusoids that may be graphically edited
Eyesweb - excellent (windows only) modular program for real-time video processing and analysing.
Processing - cross platform tool for writing digital multimedia application
Here is a good site with many links
BASIC Stamp - Microcontroller
Soundscape studios - Trondheim based company, deals with hardware audio-solutions, special speakers etc.
electrosound - Swedish based company selling special speakers and other stuff
tapeline - ressource for audio cassette tape, blank tapes, loops etc.