I don't do yoga, but Alternative Apparel's Move collection makes me want to. The L.A. based company started out doing basic t-shirts and sweatshirts in soft organic cotton. They have since evolved into fashionable ready-to-wear knit and wovens in their signature vintage inspired fabrications. A few years ago they launched "Move," a collection of comfortable, easy to move in pieces that look just as great at the yoga studio as they do at Trader Joe's.
I don't think this collection is as performance driven as I would need it to be to actually work out in, but I would love to add these pieces to my errand running wardrobe, especially come spring time.