Here's just one example---so I didn't know if I was going to nurse my second baby as I wasn't able to nurse well with my first so I signed up for the formula companies FREE coupons (they call them "checks") which vary in value between $5 and $10 OFF cans of formula powder.
I ended up NOT needing these coupons which will continue to come in the mail until my baby is a year.
People sell these coupons on Ebay. Which I think is tacky. I didn't want to just throw them away but I also didn't want to just give them to someone to resell. So instead I posted them on craigslist as a TRADE for someone who has baby scrapbook stickers they don't want/need. The amount they were to trade me was left up to them, I wasn't picky. And I met a lady who was SO generous with giving me stickers I wanted to pass this idea on to you!
You might not have formula coupons yes I know, but you may have stuff laying around the house you could trade. I have better luck making trades than in outright selling things on craigs so maybe you will to!