Root Check is a very simple tool for checking if you have root access on your device. When you open it for the first time, it will let you know whether your device is rooted.
If not, Root Check has a number of tips for rooting your device. Because the rooting process is specific to each type of device, this features leads you to other websites where you can find help (such as XDA-Developers).
Root Check also shows you which of the apps you have installed could benefit from root access. There's also a list of apps exclusively for rooted devices which you can download for free.
Root Check is a very interesting app if you want to root your Android device, even though you should probably already know whether your device is rooted or not.