GMail Drive creates a virtual filesystem on top of your Google Gmail account and enables you to save and retrieve files stored on your Gmail account directly from inside Windows Explorer. GMail Drive literally adds a new drive to your computer under the My Computer folder, where you can create new folders, copy and drag’n'drop files to.

With the size of GMail accounts increasing so much lately (mine is currently at 2.5GB+), this could be pretty useful for moving files around.