Why cloud is so popular now? Why it can be useful for you? My colleague Pavel Klimov wrote one more article "Genetic Cloud" that shows you how you can use Amazon EC2 for calculation tasks.
Of course, this example is very simple (it using usual C# program) and you may consider to use more powerful grid computing frameworks to receive full advantages of distributed calculations.
But even if you are far from such tasks in usual job and did not have a lot of experience in area of distributed calculations you can easy host your calculation application at hardware that can be unavailable for you at this moment with the help of cloud (Amazon EC2 in our example).
Just few minutes and your application is running at very power hardware while your computer is free. And moreover you pay only for short period of time when hardware is busy.