I strongly recommend L-Carnitine supplements to people trying to loose weight.
Basically L-Carnitine increases the rate of which the liver Oxidizes (burns) fats. and has been shown to lower blood triglycerides and cholesterol by increasing fat utilization. I recommend 2,000MG daily taken twice a day (so 4,000MG in total). WARNING Do NOT take if you have a active liver or possibly kidney disease or diabetes.
I've been drinking Green Tea for a few months now, and it gives me way more energy than coffee ever did, they DO have it in pill form but I have yet to try it.
Well besides a good multivitamin, many people and sources I know also suggest a B Complex supplement as dieters tend to be deficient in these because they, B12 especially, help in the metabolism of body fat.