I use a software package called 'interior designer 9.0'

HI -- I think the best why to design a kitchen is with a kitchen designer . I use to do kitchens and I did it all by measurements and drawing the plan . I have seen costly mistakes made with just relying on a computer site plan . You could use a web site to help you get some ideas on the way you want things to be, but using a certified kitchen designer is still the best way .

You can try it yourself - but pro's are pro's for good reason !! It's not as simple as it looks and there's loads and loads of guidelines to adhere to and then you want it to look good too !
If you don't want a designer in your home helping you - ie if you are too busy to schedule one in - then consider using someone who designs remotely ! :-)
http://www.houzz.com/pro/oneplan/oneplan