I agree with everyone's recommendations. I have tons of great yoga tapes and they all have different things giong for them. Ali McGraw's tape is wonderful; great stretching, good Hatha yoga, very relaxing. Bryan Kest's tapes are super challenging and will have you sweating and working hard but he always keeps you focused on SLOW deep breathing which keeps you oddly relaxed.
Rodney Yee and the Living Arts series is terrific, you can find a tape for any frame of mind: strength training, upper body, lower body, flexibility, meditation...very thorough and great variety.
I also have to suggest a lesser known tape with a special type of yoga; Kundalini or Chakra yoga. There are 2 I love. One is actually called Chakra Yoga and it introduces you, amidst the gorgeous Malibu Hills scenery, to the wonderful feeling of a truly unique yoga experience. Kundalini yoga deals with the coiled spring of energy believed to be wrapped around the base of your spine, and allowing that energy to flow upwards through all the chakras. Sounds out there, I know, but it's almost magical, the way the poses and chanting effects you. My favorite Kundalini video is by Gurmukh, and is called, simply enough "Kundalini Yoga with Gurmukh"! That one is absolutely amazing. You will sweat, you will feel like you meditated for an hour, you will stretch...it's just phenomenal. You have to have an open mind and an open heart but with Gurmukh's wonderful guidance, sweet relaxing voice and the beautiful Hawaiian scenery, you'd fall in love with this tape. I can't imagine, personally, a more perfect yoga video.
So, just had to chime in with my favorites, too. I can't believe the explosion of yoga vids out there, and a lot of them are by people who just learned yoga recently themselves and have no business teaching. The ones we have recommended though are by experienced teachers who truly believe in the ability of yoga to exercise and train the body, mind and soul.