Choosing cabinets is time-consuming, but designing an entire kitchen is downright difficult. Even with layout programs, such as Google SketchUp, that let you draft your own blueprints, having such a plan doesn't mean it can be executed. Or that you can afford it.
The easier way is to find a line of cabinets that you like and can afford, and then work with the in-house designers at a retail store. These pros use cabinet companies' software with exact dimensions, model numbers, and prices. They also have the experience to foresee and resolve any fit or installation problems—before your cabinets are delivered.
Stores and manufacturers often provide their design services at no charge, but be sure to ask first. Likewise, ask whose measurements will be used; most cabinet companies insist on taking their own, on-site, before a design is finalized, but a home-center designer may rely entirely on your measurements and leave you responsible if there are any errors.