Guess I'll be the wet blanket here, but I'd keep it simple and cheap (minimal investment) til you know this promo stuff will sell. Maybe waterproof (vinyl, mylar, polyester) stickers or decals for people to slap up around town, to promote the site. Cheap pencils or pens with the URL engraved on them, to leave here and there. Maybe business-card or postcard sized blurbs to hide in conservative books in the library.