Great suggestions already. Here's my list:
-Little People were the first thing I thought of. We got our first set before my oldest turned 1, and the kids all still play with them (even the 8 year old on occasion), so a great value for how much they get played with. Lots of different sets to choose from and mix and match.
-Simple puzzle - Melissa and Doug have some nice ones
-Play kitchen, baby doll stuff (strollers, cribs, etc.), vacuum, etc. - pretend play is big
-Very basic art supplies - big chunky crayons and some paper
-The Playskool ball popper ( http://tinyurl.com/koymau ) and the Fisher Price piggy bank ( http://tinyurl.com/la7fpt ) were also big hits
-For books, sturdy board books would be best, as well as some lift the flap or other interactive type books. I personally hate the ones with buttons that make noise, but lots of people seem to like them so try some out and see how you feel about them. Unless you really have specifics you'd like to add to your collection, I think just telling people books and letting them choose their faves works pretty well.
Enjoy - that's a fun age!