Final Fantasy VIII - Selphie/Irvine, please. I haven't found any doujinshi I don't own with this pairing in about a few years, and I really want to expand my collection.
Harry Potter - Anything James/Lily, paticularly anything by Warabi of MT--especially Lune #1 and #2. I wouldn't mind Draco/Hermione or Harry/Hermione doujinshi either. If Luna Lovegood doujin exists out there, I'd kill for it, too.
One Piece - Cute, fluffy Nico Robin doujinshi; any pairing with Robin is fine by me. Anything that isn't hentai is hard to come by, though if the hentai doujin has good art, I might be willing to buy.
I'm willing to trade doujinshi from a variety of series (Death Note, Lord of the Rings, Pirates of the Carribean, FullMetal Alchemist, Revolutionary Girl Utena, X, Tokyo Babylon, Final Fantasy, and a few others) if you have something that I want. I'm also willing to pay via PayPal.
If you're possibly interested in a trade, you can find my ebay feedback here. My feedback score is 65, with 100% positive rate for both buying and selling.