Yoga Videos: Adriene has an amazing collection of yoga videos and her 30 days of Yoga series is especially awesome.
Fabletics: At the risk of being a corporate shill, check out Fabletics by Kate Hudson if you're into the fashion side of yoga. My wife swears by their clothes and she said I have to plug their Instagram account which has some great looks.
YogaUOnline: One of the best resources online for yoga education. Great tips on how to use yoga to help a large number of ailments.
Do Yoga With Me: Another great site for yoga videos, classes and lists of poses. There is simply a ton of content on here for free and they also have a great blog and community.