Barring replacing your current dishwasher altogether, Treehugger has some simple tips to maximize the efficiency of what you have. Simple things such as using less dishes throughout the day and skipping the pre-rinse cycle are easily done but just as easily overlooked. Read through them here.
We are fortunate to have the GE Smart dispense dishwasher in our kitchen. What this particular dishwasher has is the ability to hold an entire bottle of dishwashing detergent in an internal reservoir. With the detergent readily available, built in sensors monitor the hardness of the water and amount of dirt on the dishes to dispense the appropriate amount of detergent and water, using only what is needed.