3DTutorials.sk a website dedicated purely to tutorials involving all kinds of digital art and cover very basic themes like use of colour, shade and lighting, compositing, composition and basic art theory. For the most part you are shown a picture and then they explain in baby steps how they achieved that look. Expertise wise it sort of picks up at the point where you've learned what highlighting and shading are and how to do them.
3DTotal.com More concept art and galleries from digital masters along with some excellent tutorials that more often than not actually avoid the annoying tendency towards showboating instead of educating, things like:
Title: Learn to model and texture this earth elemental!!
Step 1: Model the earth elemental
Step 2: Texture it.
No, more often than not, they're useful. Like the previous one, some knowledge is assumed, like being able to create primitive objects in a 3D program and manipulate them to some degree.
Pullbox - DRM free comics in either CBR or PDF format. There aren't a huge number of them there now but what there is is good. I think... I'd know better if I could buy the blasted things but for some unspecified reason I can't confirm payment.