SynthMaker

i found this ace software to make your own vst instruments and effects

http://synthmaker.co.uk/

its very simple to use if you want it to be just stick oscilators and envelopes n stuff together but you can also edit it a bit like reaktor and after that, a bit like max dsp and after that C++ code

you can get a fully working demo from the site the synths you make with it make a kind of random glitchy noise every few seconds but it gives you well enough time to sample the bits your after

Have Fun!