Can a Motorola Droid be in Landscape mode on the Home Screen w/out sliding out the keyboard? It's all in the title, but again for clarity: Is there any way to make my Motorola Droid  use Landscape mode on the Home Screen without sliding out the keyboard?
Yes, this is accomplished through the use of 'Home Replacement' or 'Launcher Replacement' apps.

Check out either 'ADW.Launcher' or 'LauncherPro'. Both are fantastic (and free) launcher apps that will not only make your launcher/home screens smoother, but also allow full customization, such as enabling screen rotation without sliding open the keyboard.