PowerFX has just released the Mac VST version of their SoundShuttle plug-in (a version for Windows VST hosts is already available). With it, samples and sound effects can be auditioned directly from within any Mac OS X VST sequencer, giving users the ability to preview sounds in their composition before buying them. An Audio Unit version of the plug-in is expected soon as well.
SoundShuttle logs you into the entire PowerFX online database for instant access of thousands of quality sounds and samples. Users can buy credits, obtain account information and even access their personal page (storage for purchased sounds) all from within SoundShuttle. The plug-in streams hih quality audio in real time.
SoundShuttle is sold on-line for $19, which includes 10 sound credits so you can start downloading sounds right away.