Psycle is a Music tracker (like FastTracker 2 or Impulse Tracker) combined with plugin modularity. It supports its own plugin API, the VST2 plugin standard, and a tracker style sampler playback.
jvaptools provides a library and examples for rapid vst-audio-plugin development with Java, based on Steinbergs VST interface and the sourceforge project jVSTwRapper.
IC.J.VST ("Intra-Actively Communicating JavaVST") enables you to create innovative VST audio plugins: "Intra-Actively" means that the single plugin instances can exchange any form of data - what opens a lot of new perspectives and possibilities!