there is eucalyptus in parts of california that has been introduced,it has also been introduced into alot of asia,i'm sure there are several varieties.back on the subject of locust,honey locust,(glediitsia triacanthos) is the locust that has thorns and is not a nectar source as far as i know,black locust(robinia pseudoactia) is a honey tree and doesn't have thorns.there are ornimental honey locusts that do not have thorns.both are good fire wood,and good for fence posts.
Update on the Simpson's Honey Plant. The bees seem to love it. It's not a particularly pretty plant, but good for addition of green to the perennial garden. I didn't think it would bloom the first year, but it did. The tiny little flowers are a rosy brown color, barely noticeable, but the bees think they are just great.
Nobody has mentioned the tulip tree (also called tulip or yellow poplar, although it has nothing to do with the poplar, a willow relative, but belongs to the magnolia family).
It is a beautiful tall tree that has an almost perfectly straight trunk and huge flowers that look like a tulip or lilly, The flowers produce and collect massive amounts of nectar at the base of the petals. You can in fact turn the flower over and drink a sip of nectar ... no wonder bees like it.
I'd really like to plant some Basswood (also called Linden) trees. But there are serveral varities and I'm not sure if they are all good honey trees. I know there was an article in the ABJ about Lindens maybe from the other year, but I don't know where I have that copy. If anybody can clue me in on the best basswood, that would be great!