ProXL has released Sonic Explorer, a free stand-alone Windows Explorer application with audio preview / pre-listen capabilities.
Though it's not the prettiest app, Sonic Explorer allows you to click and listen immediately due to its fast loading times. It displays a visual preview of the waveform of your audio files, which comes in handy when auditioning audio samples. Click where the "visual action" is and Sonic Explorer plays from there.
The first version loads WAV, AIFF and MP3 formats.
Sonic Explorer also features a simple "Favourite Folder" system.
