I am trying to lose weight somewhat quickly. Which exercise is best (except running because I have kind of weak knees)? Right now, I use the elliptical but my problem area is my tummy. Ideas?

find calorie/fitness calculator on the net, enter all your stats and it will tell you how many calories you need a day to maintain, take off 300-400cal off that number and thats how much you need to lose.
eat 5-6 small meals a day (eat every 2-3 hours)
5-8 servings of fruit and veggies a day
8 glasses of water
have complex carbs for breakfast - they give you energy
have lean meat (protein) for dinner - repairs muscle
cardio exercise 4-6 times a week for 30-50min, light weight training
dont consume foods that are made of white flour (white bread, cakes, past etc.), sugar loaded foods (cookies, icecream, candy etc) and nothing fried - no junk food.

you really have to find a cardio exercise that you can live with that won't bother your knees. maybe a bike? cardio is the best and most effective way to burn fat. most people lose fat in the upper and lower parts of the body first and it gradually goes to the mid section. that is how you will burn the fat. you also need proper diet and weight training. good luck to you!

Walk, Walk and walk some more. Also every evening do light weight strength excercises. Do two to three sets of about 15 reps. With light weights. 3lbs or 5lbs.
As you get stronger just do more reps of each excercise with the same weight. This enables your muscles to gain endurance, but not bulk and causes your body metabolism to speed way up.

Not sure about a quick solution. But walking is great exercise. Take the stairs. Walk to the store if possible. Mow the grass. Belly fat is the hardest to get rid of especially if it's been there a while. Oblique sit ups will strengthen the muscles and burn fat.

Walking and swimming!

Step classes - try the low impact version - you typically will burn twice the energy doing step versus running. Also make sure you do enough ab exercises to help strengthen your core, the tone will improve your posture and also keep your tummy looking as firm as it can.

My doctor discourages excercise, Just stick to the buffet, hey it works for me and the ladies love me.

The best exercise for weight loss is walking - it's what the human body is designed to do. We've evolved into the perfect walking machine.
The average person burns around 100 calories a mile regardless of whether they walk or run. If you run you'll cover a greater mileage and burn more calories in total than when walking. However, you burn proportionately more fat when walking than when running.
This is because fat requires oxygen to be metabolised. Exercising at lower intensities means that your body can take in and utilise more oxygen, therefore your body can burn more fat. Up the intensity and your body switches to burning more carbs in its fuel mix.
However, the more aerobically fit you get, the better your body becomes at utilising body fat to fuel exercise at higher intensities.
The answer then if weight loss is your goal, is to start walking at a fairly moderate pace. Gradually increase your speed and the distance covered over a period of a few weeks or more.
By gradually overloading your body in this way, it will adapt to the greater strain and you can progress - training a little harder the next time. In this way, you'll maximise your fat burning efforts and lose weight - fat - more efficiently.
Elliptical trainers provide a fantastic whole body exercise and are low impact, which will be easy on your knees. Use the upper body levers and you'll engage the large muscles in your back and chest as well as your shoulders and arms. The result is that you'll burn plenty of fat calories with each workout.
If you have time, 2-3 sessions a week of weight training for around 30 minutes or more each time will help to build muscle and increase your metabolic rate.
As far as your tummy is concerned, carry on with the aerobic exercise and you'll notice a difference in your midsection. You can't spot reduce - your body burns fat from all over your body - but many people carry more fat around the stomach area so it can take longer to notice a difference.
Ab exercises will tone your abs, but aerobic exercise strips away the fat so that you can see them.
The following link may provide you with some more information. Hope this helps!

Walk. Just walk 45 minutes a few times a week and you will DEF see results. Especially with weak knees, walking is the best!

pushing away from food

Losing weight is a simple equation: if you burn more calories than you eat, the weight will come off. Start off by estimating how many calories you burn each day using the calorie calculator http://straighthealth.com/pages/tools/ca... This will give you an idea of how many calories to eat. Healthy weight loss is 1-2 pounds per week. To lose 1 pound per week you need to create a calorie deficit (burn more than you eat) of 500 calories per day. To lose 2 pounds a week, you have to double the deficit to 1000 calories per day. You can achieve this by eating less, exercising more or a combination of both.
Guide to Dieting - http://straighthealth.com/pages/guides/d...
The 9 Week Straight Diet - http://straightdiet.com
Health, Exercise and Diets - http://straighthealth.com