Free Community Yoga classes at this nationwide chain. The new store at the Wailea Gateway plaza (Maui) offers one class on Saturdays at 9am--get there early as the space is well packed. Yoga mats can be provide though most folks bring their own. Was impressed with Jeremiah who is one of the top instructors I've ever practiced under (go Jeremiah!) :)
With such a growing popularity of yoga across the island among locals and at the resorts among tourists, a Lululemon store was certainly needed on Maui. The store sells well made yoga wear, mats and accessories (which can be a tad pricey). They offer free community class at their Ala Moana Shopping Center location as well (Oahu).