How-to: Mass Delete Spam and Trash in Gmail | The Droid Lawyer%u2122.
Here is a great tip from the Android Lawyer. The new GMail update has some annoying features; but, it also has a feature that I have wanted for some time. I used to have to go to the desktop to keep my trash folder clean. The only way to delete GMails was to check them one at a time. Ouch. Now, you can bulk delete all the messages in your Trash folder while mobile. Cool.