Can I use your art? Yes, as long as you give credit, and are definitely not using my art for any kind of commercial purpose. Web graphics, sig banners, icons, all that kind of stuff is perfectly fine and I am totally flattered if you used my stuff xD. There is no need to ask permission, just make sure you give me credit somewhere and it should be fine.
Can I print your art? Again, as long as it's not being used to make money in anyway, that's fine. This also applies to making t-shirts, which, to my amusement, a number of people have asked about xD. As long as you're not making any money with them, it's fine.
Can I color your art or use it as a reference? Sure, as long as you give credit somewhere if you end up posting it somewhere :).
Who hosts this site? Dreamhost. They rock. If you sign up with them, say alexhays referred you! (Alex is my awesome sexy friend who lets me mooch of his space).