Free / Open Source Audio Plugins:

== LV2 ==
 * Calf [http://calf.sourceforge.net/]
 * LL [http://ll-plugins.nongnu.org/]
 * SWH [http://plugin.org.uk/lv2/]
 * Zyn [http://home.gna.org/zyn/]
 * Invada [http://www.invadarecords.com/Downloads.php?ID=00000264]
 * IR Convolution Reverb [http://factorial.hu/plugins/lv2/ir]

== LADSPA ==
 * AMB http://kokkinizita.net/linuxaudio/index.html
 * Blepvco http://www.smbolton.com/linux.html
 * Blop http://blop.sf.net
 * CAPS http://quitte.de/dsp/caps.html
 * CMT http://www.ladspa.org/cmt/
 * FIL http://kokkinizita.net/linuxaudio/index.html
 * FOO http://www.studionumbersix.com/foo/
 * MCP http://kokkinizita.net/linuxaudio/index.html
 * NJL http://www.ecs.soton.ac.uk/~njl98r/code/ladspa/njl-plugins/
 * Omins http://www.nongnu.org/om-synth/omins.html
 * REV http://kokkinizita.net/linuxaudio/index.html
 * SWH http://plugin.org.uk/
 * TAP http://tap-plugins.sourceforge.net/
 * VCF http://www.suse.de/~mana/ladspa.html
 * VCO http://kokkinizita.net/linuxaudio/index.html
 * VLevel http://vlevel.sourceforge.net/
 * Vocoder http://www.sirlab.de/linux/download_vocoder.html
 * WASP http://linux01.gwdg.de/~nlissne/wasp/index.html (maintainer wanted!)
 * Nova https://tim.klingt.org/nova/download/nova_filters-0.2.tar.bz2

=== Outdated/Broken ===
 * Clipper http://quitte.de/dsp/spiced-12AX7.html
 * Lemux http://lumatec.be/joost/
 * Preamp http://quitte.de/dsp/preamp.html
 * PVOC http://quitte.de/dsp/pvoc.html
 * Unmatched http://quitte.de/dsp/unmatched.html
 * Q2Ladspa ftp://mustec.bgsu.edu/pub/linux/q2ladspa.tar.gz
== DSSI ==
 * Examples http://dssi.sf.net
 * Lars' Plugins http://ll-plugins.sf.net
 * !WhySynth http://home.jps.net/~musound/whysynth.html
 * X-Y Controller http://www.skynet.ie/~jmmcd/software/xy-controller-dssi.tar.gz