I've decided to compile a list of places where you can get stock images from, as I've recently become aware of another site that has stock images ;'D

Flickr

Please follow the tutorial, as not all photos on flickr are suitable for stock. Not everybody wants their art adapted and shared.

Deviantart

The same with Deviantart. Please read the tutorial in how to get stock images from Deviantart. There aren't many good stock images of cats and dogs on Deviantart, although you might get lucky!

Sobi

This website also has a lot of photos of cats and dogs. It isn't as fancy and pretty as the other websites, but the photos are of good quality.

Dawnthieves

This site has lots of good-quality stock of wolves.

Stock.XCHNG

You have to sign up for this website. I was skeptical that it was one of those stock websites which you have to pay for, but I was pleasantly surprised. In the sign-up area, it asks for your home address, but I just put a - as I didn't want my address in their system. Amazingly high quality stock! (Unfortunately not enough)

Morgue File

Have a look at the about page as some areas have different licenses. All images from here must be edited before use.

Websites not to go to:

Google images/Google

Google isn't a good place to look for stock. Most of it is either copyrighted or stolen.

I think a lot of it is self-explanatory. Keep to the websites I linked above. They'll be very useful when finding good stock ^.^