soundeffects can do the following sound effects on all file formats supported by libsndfile (wav, ogg, etc.): echo, change pitch, compressor, rotate, stereo boost, set surround position, and split a surround stream in its individual channels.
PyScape generates dynamic soundscapes using the OpenAL library which can be manipulated interactively via a GUI. Several CC-licensed sounds are included, such as the Buddha Machine loops and various nature sounds.