I really liked your post and I want to add some more in-depth details to what you're saying.
Before we get into boosted levels of calorie burning, let's look at base metabolic rate, or BMR. You can calculate this number here:
http://health.discovery.com/tools/calculators/basal/basal.html
After you find your BMR, a lot of times they will want you to calculate your actual calories burned across the MET scale. Instead of doing that, though, I prefer to use the sedentary rate and then use more specific, accurate calories burned (provided by your exercise equipment or online calculators) to add on to each day and find your actual calories burned.
Typical METS value for a sedentary lifestyle is 1.2, but I find 1.1 to be more accurate. So I'll do myself... in the calculator my BMR is right about 2,000. Add 10% for the sedentary rate, and I use up 2,200 calories doing just about nothing.
Now let's say I jump on the elliptical, punch in my weight, go for an hour and it ends up giving me 900 calories burned. I add that on to 2,200 for a total daily burn of 3,100. Let's say I ride a bike for 30 minutes at 12-15 mph... I can google any number of online calculators to find out how many calories that burned. For the average active person, this will give you more accurate numbers than the METS values... if you're super active though, the continual caloric burn can't be found this way, so METS values are better and those values can be found online as well.
If you can afford it, let me suggest the BodyMedia FIT CORE armband... it will give you an even more accurate number (calculated from your body heat and sweat to within +/-10% of actual calories burned) and also provides nutrition and sleep logs/analysis.
There are 2 types of calories burned... directly from exercising and calories burned indirectly throughout the day, and so 2 ways to attack your fitness regimine.
If you want to burn calories directly, you will need more than 30 minutes a day. The body doesn't actively start burning energy from fat sources for about 20 minutes into low-intensity exercising. To most effectively do this, 60 minutes of low intensity cardio (eliptical is pretty much your only viable choice) first thing in the morning before you eat anything is your best option. If you're really OCD and think you can succeed at your goals by counting calories and basically being a nit-picker, then this method will work for you.
Personally, I prefer to take a more holistic approach to things, and that means shorter, high-intensity sessions as well as strength training. I do P90X2 in the mornings (only Monday to Friday, I skip yoga) and low-intensity cardio+calistenics in the after-work hours to boost my metabolism through the rest of the evening after the post-lunch lull. The high intensity workout gives you a slow all-day burn, and the muscle building will help you increase your overall calories burned.
Something I will say, though, is if you choose the more hollistic form of exercise schedule, you will need to take up a more nit-picky diet... since you're banking calories burned on your metabolism through the day, you've got to watch out for high GI foods right after workout which can work against you. Also, you'll probably want to adopt a diet of more smaller meals to contribute to the metabolism focus of your diet and exercise plan. The direct calories burned method of exercising will burn calories as you work out, so afterwards how you eat won't make as much a difference (it still helps, though, and there is still a small afterburn)