added a new feature to Gmail Labs today: Multiple Inboxes. Created as a 20% time project by Google's Octavian Costache, this new feature allows you to expand your standard Gmail inbox with additional panes. The name 'Multiple Inboxes' is misleading, however. In reality, this new feature gives you something akin to multi-pane viewing, with your main inbox on the left and up to five other 'inboxes' on the right. These additional inboxes can display anything from searches, to mail with a specific label or from a certain sender.Google
You can use any of the standard Gmail search functions like is:starred, label:abc, or has:attachment to define a new pane.
Showing the new panes on the right works best when you have a wide-screen monitor with a relatively high resolution. Otherwise, the additional 'inboxes' take up too much space and you won't be able to read the subject lines of your incoming messages. If you add a lot of new inboxes, this will also make your screen look extremely cluttered.
You can also chose to have Gmail display the extra inboxes underneath or above your standard inbox, though this method probably works best when you set Gmail to only show a small number of messages in your standard inbox.
This new feature will surely help those of us who get a lot of email to get a quicker overview of our incoming mail, but given the name, we had hoped that it would allow us to combine multiple Gmail accounts into one, which would be even more helpful for those of us who manage more than one email account through Gmail.