Google today launched a new Gmail Labs feature called "Smart Labels," which once turned on in Settings, automatically categorizes incoming Bulk, Notification and Forum messages, and labels them as such. "Bulk" mail includes any kind of mass mailing and gets filtered out of inbox by default, where you can read it easily, "Notifications" are messages sent to you directly, and email from group mailing lists gets labeled as "Forums."
If you already use filters and labels to organize your mail, you may find that you can replace your existing filters with Smart Labels. On the Filters tab under Settings, you'll find that these filters can be edited just like any others. From there, you can also edit your existing filters to avoid having them Smart Labeled or change whether mail in a Smart Label skips your inbox (which you can also do by just clicking on the label, then selecting or unselecting the checkbox in the top right corner). Smart Lables also play nice with exisiting lables.
If you notice a message that was automatically labeled incorrectly and want to help us troubleshoot, you can report miscategorizations from the drop down menu on each message (Note: in doing so, you'll donate the full message to Google engineers to improve the feature).