Can you get a list of the RUNNING applications on Android for the purpose of activating them?
Sounds like you're overthinking it. Android goes out of it's way to intelligently manage applications and resources. When you leave an app it will generally keep running as long as the resources are available. Long pressing Home and selecting it or just launching the shortcut again should take you right back to the running app. 

Theoretically it shouldn't matter if it is still running or not, though -- every app is supposed to save it's state in such a way that if the OS kills it before you come back, it should still be able to launch back to the same state you left it in. This isn't universally applied in programs yet, but it does seem to be much more widespread these days -- presumably because the developers are getting used to the "android way."