You must belong to the SFPA in order to nominate poems and later vote for the Rhysling winners. If you're not yet a member, I heartily encourage you to join. This is one of the best ways to support speculative poetry and poets. With membership comes the magazine Star*Line and a copy of the Rhysling Award Anthology both of which are sources of excellent science fiction, fantasy, and horror poetry.
If you're not sure what poems are eligible or where to find them, check back here in early January. I'll be looking up a list of my Rhysling-eligible poems, and encouraging other speculative poets and editors to share their lists too. I know that at least a couple of my favorite poets are also on LiveJournal -- as are several editors who publish speculative poetry -- so with a little luck, that should build up to a nice tour of available options.