I know, you've seen it, right? Acumen
It's a very cool way to put your digital content online.
It’s based on PHP, MySQL and Apache. . . and contents are left untouched in web directories. This means you can access and update your metadata or bitstreams at any time, without going through the delivery software. The automatic indexer will pick up the changes. It’s very cool.
This also means that it's much simpler to get stuff in or out... and hey, if the database crashes, no big deal. The content is untouched -- just restart the software, and it will rebuild the database.
You can read all about Acumen in 'Metadata In, Library Out. A Simple, Robust Digital Library System' which was published in Code4Lib Journal in 2010. The project site is http://acumen.lib.ua.edu/project, and the software is also available on SourceForge.
Acumen software was written by Tonio Loewald. The principles behind it were developed by Tom C. Wilson... The UA Metadata Unit develops the metadata; the archivists create much of the descriptions and provide the content; and Digital Services just gets the stuff in there.
How we do that has been described in Digitization in the Real World.