if it is free b&b advertising you are speaking of, best for me was reciprocal linking with local businesses that make sense.
for my b&b, this was a local ferry service that took people across to an island for day trips and stayovers; a kayak rental and tour service; a general store (it was a destination); a couple destination restaurants, shops and museums; the town page that offered a free listing with no link back required; and a few like-minded b&b's in other areas where folks tended to be heading to or coming from.
also, sites like this one!