I'm looking for a simple document management system we can host on a corporate network. We should be able to upload files and organize them, and have the ability to access a file by a direct (intranet) URL (possibly with a login required).
Preferably open source on Linux, but Windows is also an option.
If you have a Windows 2003 or 2008 server, you have free Sharepoint (either WSS  or Foundation ) and it has Document Libraries, which is document management. It will also index the documents for search purposes.
Try a free and open source CMS. Not only do you get to host files on your network, you'll also be able to collaborate, discuss, etc. Daisy is a good example of a free and open source CMS. There will be many others.
Why not google docs? not sure about direct URL access, but it works great for me and my remote team.
I would suggest dropbox.
With dropbox, you can share folders as you like and make files public (accessible by URL). The best part is that if you install it in a PC, laptop, smartphone, everything will be synchronized, so you have everything you need wherever you are. When you install it, it will look like any other folder in your desktop, just create, edit, delete files in the folder and dropbox will synch immediately in all your computers/devices.
You can also access your files in dropbox site, just login and everything is there. You can also undelete files if needed.
There is a free version (2 GByte) and paid versions (50 and 100 Gbytes).
I would recommend Microsoft SharePoint, it's very useful for storing data and allowing collaborative efforts on projects. Also allowing for only certain individuals to access files with security log in. I got a quote for sharepoint document management and also found them to be a great research resource.
I've been using Gladinet, and it is AWESOME. Highly recommend.