Omeka is a flexible, open source web-based publishing platform used for displaying collections and exhibitions. Developed at the Center for History and New Media at George Mason University, Omeka can handle all major digital file types for documents, PDFs, images, audio and video, enabling easy sharing of primary source collections and the creation of new digital scholarship.
The software is free and available for anyone to use.
Others can use the Omeka hosted version of the software at Omeka.net or install the Omeka.org version on your own server.
Additional information on both versions can be found here.