I've really enjoyed doing coloring pages over the winter break and have found quite a few really great sites that offer printable pages. There are also two e-books at the bottom that you can get. All at no cost (Make sure the Amazon price is still $0.00).
Print out a page or two, gather your colored pencils/markers, and start coloring. Have fun!
Art-is-fun.com - Amazing site!!! I really want her Posh: Coloring 2016 Day-to-Day Calendar: For Fun & Relaxation. She shows examples colored in and they look wonderful!
Coloring-pages-adults.com - This site has a huge selection of coloring pages grouped by categories such as movie posters, books, comics, mandalas, animals and lots more.
Bramuen.net - A bunch of cute winter coloring pages to print.
Owls Coloring Book by Dover Publications - This is a book of 4 different owl coloring pages. Very Cute and quite detailed.
Mandala Circles: 50 Mind Calming And Stress Relieving Patterns (Coloring Books For Adults Book 1)
Coloring Books For Grown Ups - Sample Pack (Coloring Books For Grownups)