The Carbohydrate Addicts Diet (CAD) is like being on Atkins for breakfast & lunch, (but without counting carbs, because you're restricted to a specific list of low carb foods) and then being on the Zone for dinner. CAD recommends that dinner is a balanced meal, (which also makes dinner planning easier!), but in later books (eg The Carbohydrate Addict's Lifespan Program), the authors explain that this means 1/3 each by volume: protein, low carbohydrate vegetables, and other high carbohydrate foods.
Some people find CAD an easier low carb diet, because it doesn't require carbohydrate counting, and because it allows high carbohydrate foods at the main meal. But it also tends to lead to a slower weigh loss for most people.
The South Beach Diet
The South Beach Diet is becoming popular. Its somewhat higher in carbs than the other low carb diets - so much so, that its author claims that its not low carb at all! - Technically, you could call it a 'moderate carb diet'. Many people find this diet easier to handle, because its a bit more generous with the carbs.
So which low carb diet is for you?
Dr Atkins New Diet Revolution, if you're looking for faster weight loss
Protein Power if you want a diet similar to Atkins, but slightly more generous.
The Zone, if you're into sport or exercise and need more carbs
The Carbohydrate Addict's Diet for a relatively easy introduction to lowcarb dieting
The South Beach Diet if you want to try a less strenuous approach to low carb dieting.