Yoga Pradipika is the one of the best sources available online to learn Yoga Sutra of Patanjali which is the the best and the foremost yoga scriptures of pre-vedic era which has been translated into many languages many times. In sanskrit alone there are more than 100 commentaries available online.
In this website, you will have a detailed commentary of yoga sutra along with sanskrit original text, translitration, translation along with commentaries of notable autors like, Maharishi Veda Vyasa, Swami Vivekanananda and Osho. One could have deeper study of the scriptures here. A Great place for an yoga lover to visit.
Moreover, you can have all yoga scriptures translated. Very good yoga blog is available. Yoga Forum should be worth mentioned here.
The concepts of Hatha yoga, Raja Yoga, Laya Yoga, Kundalini Yoga have been explained in depth.
On the practical aspects, you can have guided yoga videos, meditation videos and DIY stuff. One could find everything about yoga here.
Yoga Pradipika