20/20 software in the hands of a comptent kitchen designer.

If you're already experienced with drawing on a computer, choose something that works in a familiar way. I started to use Google's Sketch-up, which is free, but it works so differently from the design programs I'm used to that it was easier, if less impressive, to stick to what I know.

If you're not already happy drawing with a mouse it might be easier to use a pencil. That's the way I learned :) I can recommend Bienfang 8 squares to the inch graph paper, which comes in drawing sized sheets (22", I think).

You can cut your sized pieces (appliances, cabinets, furniture) out of graph paper too, and use a dab of glue stick to put them in place. There's an advantage to that. When you butt up the graph paper furniture you have more than a pencil point width between the individual pieces, which is similar to the amount of space that's taken up just by putting two pieces side by side.

Good luck :)

Ikea has a cool kitchen layout planner. Of course, it only has ikea-sized cabinets, but it can give you a good idea of what you want or how different layouts look.