Dom3 and Futurecast
I've recently bought the book "The Art of Perspective" by Phil Metzger. I plan to follow up each session of reading with painting or sketching in that technique. What I've read so far is spot on, and very clear. I would recommend the book if you are feeling some self-learning coming on.
Lately, I have spent much of my time on the concept art critique center forums and found myself repeating many of the same things. I also realize that there are many theories and techniques that I have picked up over time that I now rarely employ in my own work. I've decided to commit time to these techniques and write up as I go. In the interests of both retaining knowledge and sharing it, I will be painting a series covering the techniques and principles I have learned, and will be writing tutorials as I become comfortable with each technique.