Yoga is excellent for improving flexibility, circulation and concentration.
Depending on the positions and sequences used, it can provide a low-impact way to elevate your heart rate. I am not familiar with many of the sequences, but I do know 'Salute to the Sun' does this quite effectively.
For weight loss, you may want to look into additional aerobic exercise, as yoga alone does not give you enough of a cardio-workout. Yoga-lates is something which I am yet to try, but have heard marvellous things about. As the name suggests, it combines yoga and pilates into one routine.
Local gyms and community centres often run classes such as these, where you can learn the sequences and correct ways of doing them. Once you've learnt these, you can do them yourself without having to rely on a tape. Getting pilates or yoga instruction from a DVD/tape poses the risk of developing incorrect techniques, which may lead to injury or reduced efficacy of the exercise.