This is birthday party season for us. My daughter's 3rd birthday is coming up which means most of the children she is good friends with also have birthdays coming up. Last year (when all her friends were turning 2), my daughter was in a stage where she loved to paint herself. Her favorite book was "I Ain't Gonna Paint No More" a story about a little boy who paints all over everything. So we gave many of her friends that book, lots of paints and some paper.
This year, she loves to play in boxes. They are boats, rockets, beds for her animals, houses, whatever she things of. So this year, all her friends are getting a big cardboard box, the book "Not A Box," MakeDo kits and Rolobox. "Not A Box" is a story about a bunny rabbit who imagines a box is a mountain, a robot, and all sorts of things. MakeDo kits include hinges, connectors to make box creations just a little bit better. Rolobox are wheels to add to cardboard boxes.
http://mymakedo.com/creative-play
http://www.harpercollinschildrens.com/books/Not-Box/
http://www.rolobox.com/