Craigslist.org
Most people already know about Craigslist, but just in case this is a great way to find things you need locally. Often they are used, but the ads will tell you if they are not. This is also a great way to sell your own things and make money. People sell things VERY quickly on Craiglist. I have a friend who sold her car the SAME DAY she posted the ad!
There is also a section for free things--which can be very awesome. Sometimes people don't want the hassle of waiting to sell something so they post it for free.
Just be sure to exercise precautions when using Craigslist. There are a LOT of scammers out there. Read Craigslist warnings: http://www.craigslist.org/about/help/
Freecycle.org
This is a great site to find and give FREE stuff! It is similar to Craigslist but entirely free! Who doesn't like free?! It is a yahoo group network so you will need a yahoo account and will have to join and wait to be approved. Simply find your local group and sign up and get free stuff!