Similac and Gerber both send out coupons for formulas but Similac actually sent me bottles, coupons for bottles, and sample cans of formula. You don't receive any of the coupons or anything until you are close to your due date. I just googled free baby items and a ton of pages had info on what sites to go to for free items.
Most of the major manufactures will send you free samples and coupons if you contact them via email or their website.
Also, coupon in is a fantastic way to get free and inexpensive things. If you have a Target near you, you can stack coupons and get great deals and free stuff.