If you're into the Yoga Sutras of Patanjali, here are two great online resources shared by our friend Perry in the Wednesday night Meditation and Yoga Philosophy class:
1. Raja Yoga, The Yoga Sutra's of Patanjali. by Shri Yogacharya Ajita.
2. From the Arlington Centre, The Online Companion to the Yoga Sutras of Patanjali.
Thanks Perry! Jai!