Originally Posted by scott_
There is an option setting for that, but it does not work for your home screen. Its portrait only.
Check to make sure the Auto-Rotation is enabled from the drop-down status bar. If it is, then it should work - unless, of course, you're using a custom UI.
edit: The above sounded odd to me after I re-read everything.
If Auto-Rotation is enabled, but you're using the stock UI for the Mesmerize, then the home screen with not rotate into Landscape mode. However, if you're using a custom UI (such as GoLauncher, ADW.Launcher, etc.) some of them have an option to enable Landscape mode for the homescreen.
Other than that, only a few Android phones have the capability to go in to Lanscape mode using the stock UI. That is more of a Tablet feature.