Free online drawing classes are available at Drawspace.com, Thevirtualinstructor.com and many other places across the web. Artyfactory.com is also a great resource for specific lessons on perspective and style.
Drawspace.com walks you through 21 lessons, offering drawing prompts along the way. Only 10 of these lessons are free, and the others become accessible once you buy the upgrade.
Thevirtualinstructor.com offers many lessons on drawing faces and shapes, different perspectives, and using different materials such as charcoal, pencil and pen. A few courses are available for free, and if you choose you can open all the classes for just one dollar with a special promotional offer, as of July 2015.