Google introduced yet another feature to its Gmail Labs program today: multiple inboxes. While its name can lead to some confusion, this new feature won't give you the ability to have more than one account open in the same Gmail window, but rather to expand your standard Gmail inbox with additional panes displaying anything from searches to mail with a specific label or from a certain sender.
Users can configure exactly what they want to see as well as set the number of messages displayed and the positioning of their panels. Those seriously into filters and labels will certainly find this useful. And even though this new feature is not meant for users to combine multiple email accounts into one, that doesn't mean you can't work your way around. Specifically you could set Gmail to check mails from other POP access enabled mail accounts, have these messages automatically labeled and archived so they don't appear in your Gmail inbox, and then create a pane view with that particular label.