Gmail’s mobile interface just received a welcome update; you can now sign into multiple Gmail accounts, set a mobile signature, and set your vacation message from your phone.
The biggest change is the support for multiple logins through the mobile web interface. If you’re a Gmail power user that has to stay on top of multiple accounts you can now do it from the convenience of your phone. In addition you can set a specific mobile signature and access your vacation message to create, edit, or toggle it off.
Introducing Multiple Sign-in and Preferences on Gmail for Mobile [The Official Gmail Blog]