Thanks to Slog tipper Maggie for this one:

There’s a bookstore in Portland, Oregon that will take your Kindle as a trade in for store credit. Microcosm Publishing are running this offer to the end of the month, and it’s only good at their store (mail-in not accepted)...The offer is for either $139 or $189 in store credit (not cash), and it’s only good for the Kindle.

A few years back, I wrote up five great books from Microcosm that saved me from an otherwise drab collection of fall titles. If you're going to trade in your Kindle, you should start with those.