Richard
Michael Cantor wrote above:
I'm surprised that nobody mentioned a thesaurus or a rhyming dictionary.
I have a contemporary Webster's New World Rhyming Dictionary which I use regularly, but my real secret weapon is a dog-eared copy of Walker's Rhyming Dictionary, which was printed in England in, I think, the twenties or thirties (it is undated) and I purchased second hand at the old Strand in Manahattan in the fifties. It describes itself as a Dictionary..."..in which the whole language is arranged according to its terminations". Basically it is a backwards dictionary (I don't think these exist any more) in which words are in reverse alphabetical order, and while it is a pain-in-the-ass to use - you have to think of all the possible word endings that could fit your rhyme on your own - the volume of words it contains dwarfs any other rhyming dictionary I have seen, and it is a great source of ideas.
Try
www.alibris.com They can locate many out-of-print, used or rare books. I find a lot of rare collector books through them.