How do people make the art on Deviantart.com?

A photograph was taken of them and they are then heavily photo shopped and edited. :) x

with pen, marker, paint, pencil, oil pastels, crayons, etc.

I love deviantart :) Just from personal experience and talking to other artists, a typical drawing might start off on paper with either a regular or a red pencil. You then would scan it in to your computer, save it as a jpeg and open it up in Photoshop or some type of art program like Corel Painter, like I have. If you're in Photoshop, you can get rid of the red and keep more definite lines. In Corel, you can't do that, so you'd just have draw in pencil. In Photoshop you can use various textures and layers, although the easiest way is to paintbucket-it and use the "paintbrush" to high;oght things and add depth. Thankfully, there are also a lot of tutorials on how to do that :) Some people also use watercolors or acrylics and just edit them if the pictures are under the "traditional" category, and others just start drawing on the computer. Either way is good. Have fun!

they draw it then either scan it in.. or take really hi-quality pictures

There's no definitive way to define how they make art. I looked at the kidchan things, and those were done with watercolors. Others that you say "definately aren't hand drawn" are probably done with computer programs like Corel Painter Essentials or Photoshop. It takes a lifetime of practice to get this good.

Painted ^_^

Most of them sketch it on paper, scan it, and then add textures on Photoshop. Kidchan does a lot of mixed media. She uses PS, OpenCanvas, and Painter, and traditional media. I think she has a tutorial up? cellar-fcp does his stuff on Photoshop too. He uses the default brush with only opacity jitter on. fabo-arts, traditional media. Generally if you go through the artist's comments, they'll mention how they do it. If not, they will at least mention the media they use.

With a tablet, pen, pencil, colored pencils, markers, watercolor etc etc