Docuter is a free online document host that launched in early January. Like Scribd, Docstoc (which is currently down), and others, it lets you upload documents from your hard drive or a URL. These can be viewed on the site or embedded in Web pages like what I've done below.
Docuter's claim to fame is that it supports "over 200" different types of documents (here's a list). This includes image files, and soon it will include audio and video files. Like Scribd, it lets you upload files of any size, which is nice for uncompressed, image-heavy PDFs, compared to Docstoc's 50MB limit.
The technology is built on top of the Ajax Document Viewer, a service companies can install on their own servers for hosting documents internally or with clients. Coming soon will be support for adding annotations and redactions on top of the document. These will be stored on Docuter's servers and will be separate from the source document. Users will also soon be able to lock down a document to keep users from saving and printing.
If you're looking for a social document-sharing experience, Docuter may not be for you. It does not have a catalog of publicly published documents, or a way to search through anything Docuter members have made public. It's wickedly fast though, both for uploading and processing. The two PDFs I uploaded were ready to view (and share) immediately, which is handy in a pinch.