Jan Brett, author and illustrator of On Noah's Ark, The Mitten, and the Hedgie the Hedgehog books such as Hedgie's Surprise, has some new color flashcards up for your preschoolers!  I love the printables on her web site, but they are very ink intensive!  You can laminate the cards with some clear Contact Paper to make them last a lot longer, though.  In fact, I just gave away some flash cards I made around eight years ago when our oldest was in Kindergarten!  :)