Want to know how the eventual, inevitable implementation of app multitasking on Windows Phone 7 will look? Wonder no longer: it's cards, which seems to be the way a lot of guys are going after webOS showed how to do it right a couple years back, and it looks hot. To see this in action on WP7, simply hold the back button and you'll get a card-like view of all running apps. Pick your app and you're back where you left off in that one. You can multitask even in games, have Slacker playing in the background, and if you press a volume button while on the home screen you'll get a quickie interface for changing track, pausing, and playing.
Microsoft indicated it didn't previously allow for third-party multitasking due to battery life concerns, but those concerns have been mitigated -- somehow. We're not sure of the API-level details that's letting all this magic happen, but we'll look for those later. All we know right know is that it looks great and we can't wait to try it out for ourselves.