This is quite a new development, SonicBirth (the AudioUnit design software) has been recoded as SonicBirth2. Its no longer OpenSource, however it currently is able to output 64bit AU/VST's on the mac side, and 32bit VST's for Windows.

All in a cool MAX/MSP- PD visual programming environment.

Currently a very cool aspect of the software is that it allows 1 sample feedback, so it runs everything without an audio buffer.

I have tested 64bit AU's run very well on LPX.

For more info check out www.sonicbirth.com

If you are more into coding SonicBirth allows you to see what your DSP code will look like in C++ and also the LLVM compiler. Very cool.

Next major developments will be a better UI, and most probably a sampler/buffer plugin.

Just a reminder that the software is OSX only, so if you don't have a Mac you may want to talk to a guy called Tony to fix that up! ;-)