I’ve discussed some sites already, but I have to get in just a few more that have helped me and may help you.
Lynda.com
This was the first online learning site I ever chose to throw my hard-earned cash at. It has a fantastic variety of tutorials, the majority of which are overviews of various software packages. It’s a great site, but you won’t get nearly as much out of it if you don’t own the software you are studying. With Lynda you get “all you care to learn” tutorials for one monthly fee. I am of the opinion that I learn better on the Udacity/Udemy sites where you have actual quizzes/projects, not just watching someone else tell you what each button does. I haven’t tried every Lynda course, though. Some may be set up in a more hands-on system, but there is no way to interact with the instructor.
A couple more I haven’t used, but want to mention:
Treehouse.com
SitePoint
On to the “art-oriented” tutorials.
Craftsy
Much like Udemy, Craftsy is primarily a “Pay to learn” site, and offers the same one-on-one interaction in the comments. But, frankly I have found more interaction on this site; people want feedback and critique on their art. I found this to be a friendly learning space, and it has many free classes. It also has coupon codes in your e-mail box almost every day, so think about which e-mail you want those to go to when you make your account.
Pencil Kings
I found this site by accident when searching the web for art resources, and I’m glad I did! It offers a great set of free “delivered to your e-mail inbox” tutorials. For a monthly fee you get access to many more. I haven’t taken the time to go through all of my free tutorials. It seems to focus on solid sketching fundamentals. They are always of a very encouraging tone! I believe you get to interact with the instructors as well.
Chris Oatley
This brilliant artist quit his job at Disney in order to start an online teaching school. He is passionate about teaching, passionate about art, and his classes are real “classes”; you have a lot of one-on-one interaction with the teacher, and get out of it what you put in. I haven’t taken one of his classes, but a close friend did.
Here are some other places to find good art tutorials:
deviantART
Ctrl+Paint
YouTube
Basically anywhere you can search for a tutorial, you will find some. But to improve, you just have to spend time doing the thing no matter what it is!