The Snohomish County Reusable Materials Exchange lets you sell, give away or trade things you don't want with people who do, like an online garage sale. There's lots of free stuff available, plus it's good for the environment. You can also post requests for items that you need.
The site works like a classified ad section, and it's free to use!
You can post listings of items and materials you wish to get rid of or browse for those currently available in your area.