Sweep supports LADSPA effects plugins, including:
the Computer Music Toolkit by Richard Furse, containing high and low pass filters, compressors, delays, and a port of the popular Freeverb reverb unit.
SWH plugins, many useful plugins by Steve Harris, including overdrives, comb filter, ring modulator, pitch scaler, chorus, flanger and various distortions.
more listed at ladspa.org
Currently there are over 70 free plugins available, and more are being worked on. If you are developing audio effects, LADSPA is a very easy standard to write for as it allows you to concentrate on the effect function and requires no user interface programming.
Sweep automatically finds LADSPA plugins and builds simple user interfaces for them.