Craigslist and Garage sales. Also check Kid to Kid and other baby resale shops in the area. Babies are NOT hard on furniture. I found a glider and ottoman, changing table, and crib very easily. They were high end and in great shape.
I did buy a new mattress for the crib, that's my personal preference. I feel like mattresses are very personal.
So many new Moms get almost frenzied and spend incredible amounts of money. I remember going to a babyshower for a young lady that was still living with her Mom, on her "wishlist" was a $700 crib and that was just the start. It was like she had gone through Babies R Us and just selected the most expensive of everything. I'm way too money conscious for that :)
Other ideas -- my friend recently purchased a portable crib -- instead of a full sized -- because she wanted something she could roll into their bedroom, but didn't want a bassinet. She found it on Amazon and the price was right.
The only thing I won't buy used is car seats, since they expire and you never know if a used one was in an accident. I like
http://www.albeebaby.com/
and
http://www.hipmonkey.com/ Hip Monkey is special. This is run by a mother that lost her child from a car seat that didn't hold him. She has a charity to donate carseats to families that need them, and raise car seat awareness. So, you buy something you need and the profits go to a great cause.
Oh. Some unsolicited advice. Go look at strollers in person and think about how well you can hold the baby and fold it up, lift it out of your car, etc. Look at how much room it's going to take up in your trunk/back of car. I went through 4 strollers before I finally bought a Maclaren. (Light weight, easy to maneuver) I could have saved a LOT of money if I had just bought the Maclaren to begin with. hindsight!
Hope these help. Congrats on having your first.