I was going to recommend the ceramic flat iron too. I would avoid the gold or silver plate, and ONLY do the ceramic. It's much gentler on the hair, and considering your heating the heck out of your hair with the iron, I'd do it the most gentle way possible. You can now find them at some salons for about $60, and I think they're made by a company called Cricket.
Also, have you tried Frizz ease? I know you can get that at Target, Wal-Mart, etc. I've heard rave reviews about it but never tried it. Also, I would make sure you use a straightening syrum or spray before straightening your hair. Even if you're going for the Jennifer Anniston straight hair in Friends, keep in mind that they had to flat iron her hair every 20 minutes to keep it stick straight like it was.
Good luck! Let us know what works for you.