Here's an excerpt from the Overview page:
OpenCollection is a full-featured collections management and online access application for museums, archives and digital collections. It is designed to handle large, heterogeneous collections that have complex cataloguing requirements and require support for a variety of metadata standards and media formats. Unlike most other collections management applications, OpenCollection is completely web-based. All cataloging, search and administrative functions are accessed using common web-browser software, untying users from specific operating systems and making cataloguing by distributed teams and online access to collections information simple, efficient and inexpensive.
See the Features page for more details about this open source software.