With a 32 year reputation of earning Dr. Toy and Oppenheim Toy Portfolio awards, Parenting Magazine and loads of other awards, Discovery Toys educational toys are your best bet. They are not available in stores, but through home parties or online at www.toysofdiscovery.com.
I highly recommend their Measure Up Cups, 12 graduated cups that stack and/or nest. Your baby can dump and fill the cups with water in the bathtub, or sand when you go to the sandbox or the beach. As (s)he grows, there are many other things to learn. The size of the animal pictured on the bottom of each cup is dependent on how large the cup is: the smallest cup has a tiny butterfly; the largest a whale. Each cup is numbered, and gives the number in 3 different languages. I could go on and on, but that is typical of the open-ended quality of these toys.