I use Gmail for my personal email account and over the years I have ended up on mailing lists for stuff that isn't spam, but really isn't that important to me. What that means is that while Gmail does a decent job of filtering all the offers for pills to make my Johnson larger into the spam folder, I still end up wading through tons of mail to find the stuff that is important to me and I need to respond to.
Google has announced a new beta feature for Gmail users called Priority Inbox that will be rolled out to all Gmail users over the next week or so. The new feature looks at the messages you reply to and the people you email most and sets those as higher priority than others. When a message from one of those users comes in it will be automatically filtered to an important box for you to check first.
The user will also have some control over what ends up getting tagged as priority. If a massage lands in the priority box that isn't important the user can click a minus sign to show it's not important. At the same time messages that are important that don't end up in the priority box can be sent there with a click of a new plus button.