Okay kids, listen up. Uncle Dave is going to tell you how to get free graphic novels.
It really works, too. Just a couple of days ago I got someone I've never met in Georgia to send me a copy of Sky Ape. All I had to do was send her a GN in return (in this case, volume 1 of The Prince of Tennis).
To get your free graphic novels, you'll need to make use of a site called BookCrossing, at http://www.bookcrossing.com/. If you don't have a BookCrossing (BX) account yet, go over there, click on the join link over on the left sidebar, and fill out the registration. Don't worry--it's free. (And there are no ads and no junk email--BX exists solely through benevolence.) My screen name is 'superman', if you want to put that in the 'refered by' field.
BookCrossing's true purpose is to encourage people to leave books around for others to find. But it is also used for book trading. Find a few old paperback books and/or graphic novels that you have lying around and that you're never going to read again, and register them on BX. Now you're all set.
A majority of the people on BX are willing to trade books via the mail. To find graphic novels that are available for trade, go to 'search books' and enter 'Graphic Novels' for the category and 'available' for the status. (Right now there are 464 GN's listed as available.) When you find one that you want, click on the screen name of the person where it says 'set by'. That will bring you to that BXer's bookshelf. From the bookshelf you can send that BX'er a private message, wherein you can offer a trade (e.g. "Hi, I see that you have Floogleman vol. 3 on your bookshelf. Would you be willing to trade?") Then wait for that person to get back to you. If you can come to an agreement, exchange addresses and drop your book in the mail, and wait for your to arrive. When it does arrive, you should of course make a new journal entry for the book, and your trading partner will do likewise. (In the US, you can cheaply send books via Media Mail, which will cost just a $1.42 for a standard paperback, and a bit more if it's a bit heavier.)
BookCrossing operates on karma. So when you're done reading the book you get, make it available to someone else, or release it 'into the wild'. Some BXers will offer to send you a book without a trade--if so, you are karmically responsible for making the same offer to someone else.
Part of the fun of BookCrossing is watching where your books end up. My copy of Chobits, vol. 1 is hopping around in Pac10 country, while a couple of Garfield collections are being enjoyed in Iran.
Speaking of offering books, I have two graphic novels marked available on my BookCrossing shelf right now, @Large, Vol. 1 and X/1999 Prelude, each of which I will send free to the first persons (in the US or Canada) who message me via BookCrossing and request them (only one per person). The only stipulation is that you have to give it to someone else when you are done reading.
So go, and set your old graphic novels free!