If you don't mind taking a bit of a risk, you can often get a good deal at the Goodwill auction site. The sellers are Goodwill locations from across the country. The prices are usually pretty good, but the items are sold "as is" with no guaranty that they will work so there are some caveats.
First, read the description and look at the photos carefully. The sellers will
usually try to turn the device on, but they will not do any in-depth testing. If it doesn't turn on they will usually make a point of saying it's for sale "As Is" or "For parts only." If it turns on --
and the pictures look good -- you're probably okay. If they say they have done "No testing," I would assume it has problems. It's also a good idea to read exactly what's included -- most items are sold without USB cables, AC chargers, etc.
Second, check the shipping and handling charges. They can add up if you're on the other side of the country.
The usually have plenty of Kindles (of various model numbers) but those are also the most popular, so the prices are relatively high. Nooks are also pretty common and (usually) more reasonable. Other brands, like Kobo, etc., show up and often only attract a single bid. For instance, I recently got a Hanvon reader in great shape for $8.99, including shipping and handling.
I have never had a problem with an ereader from Goodwill, but it's possible, so you are taking a bit of a risk. I've bought two Iriver H320 hard drive MP3 players, and both had problems -- so it's something to consider. (I was able to fix both players, so I'm still happy.)
The ereader listings:
http://www.shopgoodwill.com/listings...1&ending=Items