"Another possibility is to go with a company that offers month-to-month service such as T-Mobile or Virgin Mobile. You can get an unlimited voice/text/data plan for $50/month, and without a contract so you can get out anytime. I haven't tried them personally so I can't vouch for the value of their data but I'm seriously considering going with them when I finally enter the 21st century and get a smartphone."
One warning I'll give in this is to check the coverage for your area, because the coverage pattern has one very important but rarely realized effect. If the coverage in your area is spotty for the service you choose, your phone is going to spend more time hunting for signal, and the surprise effect of that hunt is that your battery won't last nearly as long. As an example, I got a work phone on one network, and my wife got an identical handset but on a different carrier. Because the coverage for my carrier is better, my battery lasts three or four times as long. Trading batteries proved that it's not a faulty battery, so be aware and do your homework online before deciding.