When I am doing yoga I like a thicker mat. Usually the mats available to rent at various studios are too thin for me. I found my first mat at TJ Maxx, its this Premium Yoga Mat. I really like it, it has traction and it is extra long. People don't really like the extra long mats in crowded classes, but I like that it gives me extra room. I also really like the adjustable straps it comes with, adjustability is key.

I was also just given another mat for Easter, a Gaiam mat that has the best traction you can get with just a mat. And they are also offering a special that anyone that buys a mat also gets a free yoga video.