After seeing the running apps you should shut them down to save battery power. Touch and hold a icon until they wiggle Touch the red x to close them one at a time. Yes close them all phone , mail etc. incomeing calls and mail will still work.
I had a android app that was on the home screen that was called app killer. It shut all running apps down. Does anyone knon if there is such a thing for the I ?
Let's kill that myth right now, shall we? Killing tasks on mobile phones is bad for the system. I'm an ex-Android app developer and themer so I though I'd explain why a task killer isn't needed on a *nix-based system.
Activities
Android apps use activites to preform tasks. For example, if you use a file manager to send a picture via email, the file manager calls the send activity within an email app, passes the file name to it and the email app sends the picture.. not the file manager. This will result in seeing the email app as "running" even though the user didn't actually launch that email app.
Smaller apps
Using activites helps developers design smaller apps. A file manager app that contains every bit of code needed to do everything a file manager does would likely be so large that no one would want to install it. Developers know that an android phone more than likely has an email app so there is no need for the developer to include email code in his/her file manager to send a picture when he/she can call an activity in an existing email app to do the job. This results in a smaller file manager app since there is no need to include email code or any other code for an activity that can be done via an app that is already present on the phone. This also alleviates redundant code. When you install an app outside of the android market, also known as sideloading, the file manager app calls the package installer (already present in Android) to install the requested app.
System management
By default, every android application runs in its own Linux process. Android starts the process when any of the applications code (activities) needs to be executed, and shuts down the process when its no longer needed and system resources are required by other applications.
If you see an app running that you didn't launch, it's most likely because an activity within that app was called by another app to perform a task. If you kill the app you didn't launch, the system has to relaunch that app in order to complete the original task. This is why some people kill a task and then see it immediately running again. Constantly killing that app creates a situation where the user is battling the system resulting in wasted system resources.
Also, I believe SkullOne posted facts about killing apps on iOS being detrimental to the system performance.
Sorry for the off-topic post but I felt it necessary to prove why the best practice is to learn about the system instead of performing work based on a myth.