This highly recommended Firefox extension takes the small pile of gigabytes that the Google folks throw at you for your Gmail account and turns them into a drive with storage and music-playing capabilities.
Accessible via a toolbar button or from the menu bar, Gspace opens a new tab with an FTP-style interface. You can transfer files by highlighting them and hitting the directional arrow. Drag-and-drop is not available, but the plug-in is still replete with goodies. Uploading a file sends an e-mail with it attached to your Gmail, so you can create Gmail's native filters and folders to keep track of files you've uploaded. Deleting the file from Gspace deletes the e-mail.
Gspace also allows users to switch between different Gmail accounts, has an In-box button so you can quickly jump back to the standard Gmail interface, and supports different uses of the virtual drive. These include a Music mode, which can be used with a Flash music player to create a Web-based MP3 player, and a Photo mode that didn't work for us at the time this was written. The rest did, and it made home-to-office file transfers almost as easy as using Google itself.