I recently came across a great series of free videos and tutorials at ctr+paint. One in particular caught my eye, it applies to just about every design/art endeavor. The Principles of design are clearly laid out in this mini series (taught mainly from a digital painting standpoint but useful for all design and art practices).
This mini series is clever, easy to follow and very enlightening – even to the seasoned artist. I highly recommend you bookmark that site as it is a treasure trove of helpful design, and painting tips.