Random House's Golden Books' website has a nice section called "Print Factory" with lots of cute printables for younger ones.  Over 50 printable coloring sheet topics include:

• Learning - Counting & Shapes
• Activities - Connect the Dots & Mazes
• Wildlife - Mammals, Ocean Life & Birds
• Poky Little Puppy
• Rudolph
• Fun - Toys
• Dinosaurs

While you're there, sign up for their newsletter and take a look at some of their popular book websites - Pat the Bunny & Richard Scarry!