I moved my Steam games last week onto my D Drive. Steam has simple instructions on how to do this.
Navigate to your Steam folder. Make a backup copy of your Steamapps folder (just in case it goes belly up). Delete everything inside your Steam folder EXCEPT for Steam.exe AND Steamapps folder. Move whats left of your Steam folder (a bit lighter now) to your desired location. Run the Steam.exe . Voila !! Steam will now install all of your games on your other drive.
Take note that with Steams latest update, you can NOT install Steam in the Root Directory of your hard drive. Make a folder called Programs, Games or whatever and install Steam in that directory.
When Steam updated all my installed games disappeared and Steam did not recognize any free space on my HD, I have over 850 GB free. After I reinstalled Steam into a new directory everything worked fine. Except, I have to download and reinstall all my games again (what a pain).