Hey, are you tired of collecting a certain manga? Did you just buy volume 11 and really don't want to invest until volume 24?
If your manga is in good enough condition (No folds, no tears, minimal wear) you can take it to your nearby Waldenbooks, Brentano's, or Borders and tell them you'd like to return them for store credit.
It might take a little bit of social engineering (I use "My grandparents know I like manga, so they got me these for my birthday/religious holiday/graduation, and I really don't want them) but usually, so long as they've sold or still sell the book, they will give you store credit for the current selling value.
I've done this with Initial D and Maison Ikkoku, as well as a bunch of other manga that I bought, realized sucked, and subsequently lost the receipt for.
You do NOT need a receipt for this.
What you then will get is a gift card, valid at all Waldenbooks, Brentano's, and Borders... or Amazon.com. Since Amazon does the online ordering for Waldenbooks, just go to Waldenbooks.com, enter your orders as normal, and then be sure to enter the number on the back of the gift card when it asks you to put in gift card info. I just ordered a bunch of stuff from all over Amazon - electronics, manga, and anime - and as long as it's not from a Zshop or third party off of Amazon, it's yours.
Try it for yourself before they update their policy!
Err... I don't want to buy your used manga at normal price without knowing.
How do you know if you haven't already? If they're kept in new condition, no abuse, no wear, no dust, etc. (It's not so hard... just keep them in a bookcase when you're not reading 'em) you might be already. I might not be the only one who knows this stuff.
Yeah, I know. I meant anyone's, generally.
I've also seen some in bookstores that have obviously been read through, either at someone's house, or at the bookstore itself.
I hope they don't re-shrinkwarp the normally shrinkwrapped ones, though.