The best resource is probably The Writer's Market 2009. It is a bible for writers, in a way. Its about 20$ on Amazon. There are separate ones for poetry etc. It is worth the investment if you are serious about getting published!
I'd even say that an out-of-date edition (no more than, say, five years old) is still worth picking up if money's that tight. You'll still get enough information to find a mailing address for any magazine or publishing house in which you're interested, and you'll usually be able to zap off a query letter via e-mail.
Alternately, if you've really gotten your ducks in a row and you've set up a business as a writer (business license, tax i.d. number, the works), you could do a lot worse than go to a convention in the genre of your choice.
http://www.scificonventions.com/... might be a good place to start, but there are other options.
Check with your lawyer and accountant contacts, but being able to lump the "$240 Attending Membership" fee and the hotel room for WorldCon 2009 as a "business expense" would certainly be worth the paperwork.
