Interested in improving your drawing skills? Well you can always take more Art classes, buy drawing books, and join local art clubs - all of these are helpful in encouraging you to push your skills to the limit. However, you can also try visiting online "how-to-draw" sites for advice and information. They're often not as detailed as other methods, but they're a lot cheaper.
One of my favorites is a site entitled Drawing / Sketching. This is actually part of the About.com network, which I love because it's more than just a search engine. Each section is maintained and regularly updated by someone currently in that particular industry (or if there is no industry for that category, someone who at least has a lot of experience).
Drawing / Sketching is no different, as it's maintained by an Art teacher named Helen South. On her site, she does a good job of updating frequently and providing pertinent information, advice, and links. I must admit, I've used some of her tutorials when making take-home lesson plans for high school students. If you're an Art teacher or Art student, you should really check out this great resource.