From the FAQ: Scribd lets you publish and discover documents online. It is like a big online library where anyone can upload. We make use of a custom Flash document viewer that lets you display documents right in your Web browser. There are all sorts of other features that make it easy and fun to publish, convert, embed, analyze, and read documents.
Part of the idea behind Scribd is that everyone has a lot of documents sitting around on their computers that only they can read. With Scribd we hope to unlock this information by putting it on the web.
For libraries with limited web functionality or an outside IT department this could be a solution for those "need to get it online" projects.