An idea for browsers

So, I just started  using browsing the inter-tubes right now, and I'm a tad buzzed. I've got 7 "tabs" (their actually windows since I'm using opera), 2 fourms, two programming resources and 3 other random ones. What I think would be really cool is if there were a way to group windows within the MDI, so that I could take a group, and tile or cascade just those windows. Or, alternatively, if I have a group of windows open for one reason or aonother, and I'm done with them, I could close them all at once.