I LOVE Dover Coloring books!
They make very educational, detailed, coloring books. Many for older aged children. I love supplementing our 'books' that we make w/ pages from their books. While on our road trip, my oldest (14 yo) chose a Dover coloring book about Pioneer days (or wagon trail?) as a souvenir.
While looking for some printables online for various topics, I came across their site. You can sign up to receive an email every Thursday w/ links for FREE coloring pages to print from your computer! The pages change every week & are various topics.
I can't say enough about their books. They are quality drawings that make great supplements for unit studies or for littles. Your biggers will appreciate the details & intricate illustrations.
I just found that they also offer great looking 'kits' direct from their site...great prices & free shipping for orders over a specified amount! YAY!