Cardio is best for burning fat. A good rule of thumb is 30 minutes (more or less depending on the intensity).
Here's some good cardio workouts....
Sports Conditioning Running
HIIT Me With A Carbo Burn
Cardio Fight Club HIIT
MAX Tabata Test
Fat Burner Deluxe
Quick Cardio Crunch
Chiseling Cardio Fix
Burn Fat Burn!
Cardio Go-Getter Gobble
Also try building a little muscle. Your body has to work harder to maintain 1 lb of muscle than it would to maintain 1 lb of fat.... So you keep burning calories. This is great for keep the fat you lose off.
HIIT (High Intensity Interval Training) workouts are perfect for building lean muscle. These workouts force you to work hard in short intense spurts with little recovery time in between. The result is a spike in your metabolism creating greater after burn (the amount of calories you burn after your workout is over).
I built my HIIT workout (Core Blast) from exeecisea I found here and at ab-workouts-guide.com If you like it checkout Core Abs & Stretches, Multi-Plank Challenge, Mid-Section Drill, Autumn Abs, Drill Sergeant Mom, Extreme Plank Pyramid Challenge, Core & Glute Kicks, or P90x: Ab Ripper X they're fun and challenging.
Good luck and God Bless!