<i>Cydia, the app store for jailbroken iPhones has a backgrounder app. Give it a try. What they don't tell you is that it sucks, maybe because the iPhone doesn't really have the ram to run apps in the background or maybe because the iPhone OS wasn't designed that way, but for some reason I'm leaning towards the former as an explanation.</i><p>I found the Backgrounder app to be a great way to multitask on iPhone OS.  First of all, it gives you a visual indication on the icon of every currently running app, including the Apple ones that are always running like Phone, Mail, Safari, and iPod.  Second, it's very intuitive and easy to use, you simply hold the home button down for 1 second instead of quickly pressing it, if you want to background the app instead of just exiting to the home screen.  Third, it passes the number one use case very handily:  I can listen to Pandora while surfing in Safari seamlessly, and it almost makes my iPhone seem like a functional computer.<p>iPhone 3GS with backgrounder is seriously a powerful device, and lets me have an insight into how powerful the iPad will be.<p>Don't get me wrong, I'm not a fanboy.  I won't be buying an iPad until I'm sure it can be jailbroken, and probably not rev. 1, because I'm sure rev. 2 will have the missing features like webcam, etc.  I'm just saying that a jailbroken iPhone/iPad will be an impressive device.