CtrlPaint.com is a great resource for artists looking to crack the digital art code. A few ten-minute long videos can get you on your way to creating art in PhotoShop.
I work in Illustrator, which is a very different method, but have been wanting to try the CtrlPaint PhotoShop method. Here's my first try. I did this yesterday. I'm still using a very cartooney illustrator line, but moving toward a more painterly finish.
Click to enlarge.