Scoble likes Outlook:
Anyway, I use Outlook as my entire operating system. Seriously. It makes backing up my important files much easier than looking for a hierarchical tree inside my C: drive somewhere. Just back up one or two .PST files, and away we go (I drag any important file into Outlook at the end of my workday so that it's automatically synchronized between my two computers -- and also so I can get into it via the Outlook Web Access, so if I need to get into my "operating system" from a public library or at the airport, I can).
I use Outlook to backup documents I'm working on to a folder on the Exchange server. Its great because when you drag a document into an Outlook folder any previous copies of the document in the folder are not overwritten and you don't have to fiddle around with filenames to uniquely identify separate versions of the document. Just drag and drop, the backup is done, and you have a history of snapshots of the document for free.
Also, you can "mount" your Exchange folders in Windows Explorer via WebDAV by selecting "Map Network Drive" and then clicking on the "Create a shortcut to a web folder or ftp site" link. On the "Welcome to the Add Network Place Wizard" type in the WebDAV uri for your Exchange folders. This is the format:
where mailserver is the name of the Exchange server and myaccount is your Exchange account name. You don't need to specify the root folder of your Exchange folders, just extend the above path to any particular folder you want to mount.