And there are other options, as with VATSIM i believe you need to be online to play the part of an air traffic controller...
There are many other ATC simulators on the market which are highly realistic and gives you a good feel of being an ATC.
Some are expensive and some are free for download.
Visit
ATCForum.com
You will be able to find out about all the simulators out there. Many wannabe ATC's to help out with custom designed sectors etc.
Plus many other real ATC's from around the globe too!