No - for a non-jailbroken iPad there is no app that can do this.
However, those apps arn't really taking up system memory (RAM) as they might appear to be doing. The iPad's operating system, iOS, removes non-active apps from RAM if it needs the 'space'. Although they still appear in the multi-task bar, only the last couple of apps are, at most, still actually resident in RAM. The rest have their contexts (states) saved in the main (flash) memory so that, should a user choose to 're-activate' the app, it can be restored in exactly the same state that it was when it was last used.
Tim