About two years ago we started a project in which we we collecting several hundred recordings each week at different sites. In an instant, browsing this archive became a problem due to the difficulty in browsing files that we need to listen and look at their spectrograms to make sense. Back then I started to work on a web-based system to manage and browse the archive. What was then is now an open-source and free software system available in version 1.0: Pumilio.
Future enhancements include options for ultrasonic and infrasonic recordings, more tools, and improved archive and metadata management tools. If you are interested in testing it there is a demo available or you can download the current version from SourceForge.