If you have friends that also craft, try to plan a craft swap. You can all get together and bring your unwanted craft supplies and trade them. Invite everyone you know, such as friends, your kids’ teachers, and other parents. This can also be organized for a community group such as a church members or scouting troops.
You can take this idea a step farther and plan annual, semi-annual, or even monthly craft swap party. Everyone can bring food to share along with their craft supplies. You can even plan a craft activity to do together during the party. How about giving your craft swap party a theme and encourage everyone who will be attending to bring supplies related to the theme.
Another option might be to find other crafters online you can swap with. I have a section in my forum especially for those who are looking to swap supplies. Check it out... Swap Supplies on the Family Crafts Forum.
You might want to check out the Freecycle Network. It is a grassroots movement of people who are giving and getting stuff for free in their own towns. It is all about recycling and keeping goods out of landfills.
Zwaggle is a "national network of parents who have come together to share." On this site, you receive points by giving your gently used things to other families, then use those points to obtain "new" things for your family. You can also donate items to charity.
I ran across a site called Swaptree that I thought looked interesting. This site specializes in helping you trade books, CDs, DVDs, and Video Games with other people. This might be a good way to get new craft books!