will say I have seen some CD's on Zulily on occasion - Fuzzibunz and maybe Charlies? - and the price is fine, but I hate how much their shipping is - usually around $8.
I second craigslist. And diaperswappers.
If you order regularly from amazon, love being part of amazon mom; now I don't have to pay for Prime! I think it's HappyBabyCompany? but it's a mama that posts here a lot, does 10% off your order with code MDC10 (I think).
If you are a fabric/crafty person, I just did the Joann's app for my phone (I have an iPhone, but I think there is also a Droid version) and you get coupons to your phone daily; 50% a regular priced item, and usually they have a $ or % off your total order one active. No printing or anything, which I like.
In our area we have seasonal consignment sales, If you have anything like that in your area, it is so worth it to go! Ours are coming up in September, and I am going to score! When I was pregnant with my first, I came away with SO MUCH stuff - got at least a dozen sleep sacs (the Halo ones!) for no more than 3 or 4 dollars each, not to mention tons of other stuff. Also, new moms (anyone who has had a baby or will have in the next 12 months) usually can get in early to go through things before the general public.