There is a keyboard shortcut for moving emails to trash. By default it is "#" but you can use a GmailLabs feature to change it to something else. Unfortunately,

There is a keyboard shortcut for moving emails to trash. By default it is "#" but you can use a GmailLabs feature to change it to something else. Unfortunately, it cannot be the delete key. I set mine to "d". As far as labels go, if you don't want emails that are labeled to show up in your inbox then just set a filter on them to "Skip the Inbox". I do this with all of the emails that come from any company (Twitter, Borders or Amazon).