Tom Szilagyi has written a number of plugins for LADSPA compatible hosts (e.g. Ardour, GNU Sound and GStreamer).
The plugins (Equalizer, Reverberator, Stereo Echo, Tremolo, Scaling Limiter, AutoPanner and DeEsser) have been written primarily for Ardour but should work well with any LADSPA host.
Homepage: http://tap-plugins.sourceforge.net/