I haven't seen these mentioned yet: Spacedad s.i.c.k. Modular Plugins
They're a bunch of simple modular synth plugins--step sequencers, LFO, ADSR envelope, oscillators, clipper, etc. I find them fun and easy to use, they're good utility modules when I don't want to fire up a complicated VST for a simple task.
Each one is a separate .dll. Made in SynthEdit--so they're Windows 32 bit, not multiprocessor, you may have to copy & rename extra .dlls for multiple instances.