Well, one of the ones I've actually had fun with lately is, believe it or not, Ultima Online. It's really old, but it does have a lot of things to do and seems less like a generic hack-and-slash diablo clone like many of the MMORPGs I've played. Check it out if you want a cheap way to get into MMORPGs. And it helps that I'm playing on a free server.
Most have options to pay without creditcards, you usually get 1 month free with them and then you can add on to that with gametime cards that you buy in stores. Prices range from around $13 to $15 a month. Also, many of them have free trials, so check out Fileplanet and see what you can get.