Recently I've been using some of my free 25GB SkyDrive allowance.
As a Windows Live user you get access to 25GB disk space in the cloud through SkyDrive as well Hotmail and a web-resident version of Microsoft Office all for free.
I find waiting for files of any non-trivial size to upload (or fail to upload) from the browser to SkyDrive quite tedious. Consequently I was pleased to see there was a canny way to map a folder in your SkyDrive space to a drive letter in Windows Explorer.
It relies on you noting your SkyDrive CID (in the URL when you log into it after a cid- prefix) and mapping to the UNC path:
Full details available in the original blog post.
One note though - I found I didn't have to map Documents to ^2Documents. Just using Documents worked just fine for me.