M.L.
We have a soft square toy by Lamaze that my daughter really loved. It has different textures on different sides, and she spent a lot of time exploring it. I think ours was from Babies R Us, but here's a link: http://www.geniusbabies.com/clutcubnew11.html
I also agree that you don't need a lot. We had 3 or 4 probably to start with. One in the carseat, one in the stroller and one in the house. We would rotate which was where and which ones she was playing with and which were "resting" every couple weeks so it always seemed like she was getting new things. Correll (http://www.corolle.com/us/catalogue/babicorolle.php5) also makes some very nice and high quality dolls. They have some that are boys or gender neutral if it would bother you to give your son a pink doll. My daughter LOVES her "miss rose" and she's had it over a year with very little wear and no tear.