A huge community of artists, where you can often find very talented people showcasing and selling their art. You'll find a large variety of different styles and types - from photography to digital art, they have a lot to look at and admire!
deviantART is a website that has a community aspect to it, as well a place to garner real critique from people who have experience in the field you might be looking to learn about. Cons: The website is often filled with people who come for reasons other than art, as well as an interface that can seem overcomplicated and cluttered.
Nice resource for stock images, brushes for Photoshop, and tutorials. Cons: If this is the only place you have a portfolio, professionals may not take you seriously as an artist. I use it mainly as a dumping place for older work or experiments.