Pure Data (PD) is a real-time graphical programming environment
for audio, video, and graphical processing
It is extendable by st of plug-ins, writing object classes ("externals") or patches ("abstractions")
It's similar to Max/MSP, and it works on Win / Linux / MacOS X / IRIX
It's open source and gives you a lot of possibilities to create, and to share tools with / from other developers.
Curious?
Try these links:
::::::::::::::::::::::::::::::::::::::::::::::::::::::pd main
http://puredata.org/ (((official site)))
http://puredata.info/
http://pd.iem.at/
::::::::::::::::::::::::::::::::::::::::::::::::::::::download pd
http://www.crca.ucsd.edu/~msp/software.html
http://pure-data.sourceforge.net/
http://puredata.org/Members/hans/downloads/installers/ (((easy to install/run)))
http://sindominio.net/~caedes/debian/readme (((debian packages)))
::::::::::::::::::::::::::::::::::::::::::::::::::::::some externals
http://gem.iem.at/ (((gem)
http://zwizwa.fartit.com/pd/pdp/ (((pdp-video)
http://ydegoyon.free.fr/pidip.html (((pidip for pdp)
http://framestein.org/ (((only for windows, image-video processing / manipulation)))
http://artengine.ca/gridflow/ (((dataflow processing library)))
http://zwizwa.fartit.com/pd/sendVIMS/ (((veejay tool)))
http://www.cnmat.berkeley.edu/OpenSoundControl/ (((osc)))
http://benchun.net/flosc/ (((flash -> osc)))
http://testsite.at.or.at/hans/pd/hid.html (((hid-force feedback)))
http://www.akustische-kunst.org/puredata/shout/index.html (((shoutcast/mp3 streaming)))
http://www.interface-z.com/produits/index.htm (((hardware interface)
::::::::::::::::::::::::::::::::::::::::::::::::::::::links mix
http://pd.klingt.org/
http://m.ash.to/pd/
::::::::::::::::::::::::::::::::::::::::::::::::::::::alternative/similar software
http://cycling74.com/ (((max/msp)))
http://vvvv.meso.net/tiki-index.php (((vvvv)))