I put together an audio plugin using Juce*. Really impressed by Juce so far. I've been able to build VSTs under Windows, but unfortunately I don't have a Mac so I can't do OSX builds.
Would anyone be willing to build on OSX for me? In exchange, I'd be happy to build your project on Windows..
Screenshots / Windows binaries:
* If you're interested, the plugin wraps the OPL2 emulation from DOSBox.