First off, we want tomention the granddaddy of all scrapbooking printables sites: www.ScrapbookScrapbook.com
This site has been around a long time and has a wealth of great graphics. Originally they charged for the full size sets, but now it is all free. In addition to scrapbooking backgrounds, etc...they are print and make pop--up cards, Valentines, Red Hat Society themed notecards and more.
The printable teacher's award certificates are great and teachers will like the printable Christmas Nativity. All Free.