Here's another website, lines and colors, that I've recently added to my RSS feed reader.
They have a great variety of content relating to art.
Here's the quote from their blog:
lines and colors is a blog about drawing, sketching, painting, comics, cartoons, webcomics, illustration, digital art, concept art, gallery art, artist tools and techniques, motion graphics, animation, sci-fi and fantasy illustration, paleo art, storyboards, matte painting, 3d graphics and anything else I find visually interesting. If it has lines and/or colors, it's fair game.