Gmail's latest Labs creation is one of the best yet: panes that let you create separate inboxes using filters and labels. Anal-retentive over-organizers of the world, rejoice!
Want to have a pane just for emails from your family? Or from a particular mailing list? You can easily split up threads from different people or groups or based on different subjects or anything you want. It's a great way to use filters to turn one email account into many. Brilliant.
To turn on Panes, just go to the Labs section of your Gmail settings and turn on Multiple Inboxes.