There are hundreds of books, tapes and Websites that tout the latest and greatest diets and exercise programs. It can be very confusing. What may work for one person, may not work for another. I would advise you investigate all diets carefully and review all with your physician before starting. Be sure to review your medications with him (or her) at the same time, as some medications may react with certain foods. Stay away from fads and outrageous claims. I have searched the web and found some sites you can look at. I've included both diet and exercise.
Atkins - Low Carb
About.com's own guide to weight loss examines the low carbohydrate diet. This has been very successful for many people. The most famous of these is the Atkins Diet which recent research has shown to be safe for short term weight loss.
While dieting you must still maintain adequate nutrition. The Food Pyramid is a good resource to use to make sure you are on track.
South Beach Diet
This article from the Mayo Clinic provides some simple and easy ways to eliminate extra calories from your diet.
A collection of sites for exercise programs geared towards seniors.
From About.com's own exercise guide, the best of the web in exercise for seniors.