Gladinet no longer appears to be free. Personal use is about $7/month.

I have better experience with mounting the WebDAV address from SkyDrive Simple Viewer for WebDAV:
SkyDrive Simple Viewer for WebDAV

It's slow and clunky - but it has one great advantage.

It automates uploading to Microsoft Skydrive. Skydrive offers 25GB free storage but limits you to uploading 5 files at a time manually through your browser so until now it was a waste of space (ha ha).

You can point Gladinet at a folder and it will sent the contents up to Skydrive in the background - so you can use it for off site backup up to 25 GB!

For day to day synching i'm like the rest of the world : DropBox FTW!

and if by any chance you have not yet signed up for Dropbox please use this link - It will get both of us an extra 250BG space :) : https://www.dropbox.com/referrals/NTIzNzk1Mjk

Theoretically Gladinet should be able to mount WebDAV online storage:
In summer 2009 this function did not work with http://alternativeto.net/desktop/mydisk/ nor with http://alternativeto.net/desktop/gmx-file-storage/ .
However,
I had good success with mounting Google Docs, Google Picasa or Microsoft Live SkyDrive as local drives,
and I also could synchronize these online content.

Disadvantage:
The access to these synchronized local files is very slow, much slower than to files synchronized with http://alternativeto.net/desktop/sugarsync/ or http://alternativeto.net/desktop/dropbox/ .

A pile of poop that doesn't work. Look at the "Awards" at the bottom of the homepage to see what dubious sites have rated it. It is not the sort of software you would want on your computer. It doesn't even look like the site has been updated since May 2009 if you go to the "Compare Editions" page.

never could get it to work on my computer (Toshiba laptop running XP 3)

v1.1 rc now supports EMC Atmos Online, Box.net, Google Docs for Google Apps, WebDav and FTP, in addition to Amazon S3, Google Docs (personal) and etc.