Be careful with some of the Gaiam tapes-they seem to label everything "beginner" and a lot of them are not suitable for beginners.
I highly recommend yoga zone's dvds-they give excellent instructions and modifications for those of us who are less flexible. I also second the suggestion for Sara Ivanhoe.
If you have a dvd player, definitely try Deep Discount DVD-they have the yoga zone dvd's really cheap-some for as little as seven dollars, and have free shipping. They have Sara Ivanhoe's dvd's also.
If you have Comcast Cable, in some areas on channel eight they show Yoga Zone's television show-you can check them out. They're also on the Wisdom Channel if you have the Dish network satellite.
"I can't change the world, but I can change the world in me. I rejoice!"-Rejoice by U2