the first one's an article the other two are the most common sites on the subject. you could also look for books, D.J. Conway's Dances with Dragons is the most common one you'll find, and it's not highly recommended, though the guided meditation is good. it's hard to find books on the subject because Dragon Magick is passed down verbally from the dragons and very little is written down, or passed around outside of a clan.
feydragoness is correct, the best way to learn is from the dragons. Dragon Magick is dangerous for those who don't know what they're doing, so learn the basics like meditation, energy work and shielding, but you'll need to learn Astral Projection because dragons are astral beings, while they do occasionally visit the physical, they spend most of their time in the astral.