Cingular's national plan can't be beat for now, if you travel at all. 250 anytime, 3500 n+w, free roaming anywhere in the USA, and free long distance, plus all of the other features. Although it unfortnately appears that you can't get Cingular as they don't serve your area.
AT&T or Voicestream are probably your best bet, because they both have the cool Nokia phones...sure, with Sprint & Verizon, you can get a phone with ringtones and games, but the collection of sites with ringtones for Sprint & Verizon phones isn't as extensive as it is for the Nokia's that AT&T, Cingular and Voicestream use. And who can pass up Snake?
I'd recommend the Nokia 3360 with AT&T service, its a great little phone, and is basically the replacement for the 5165 (consumer oriented, "fun" phone, with changeable faceplates, downloadable ringtones, games). Its very easy to use. I'd recommend you buy an aftermarket lithium battery from Newegg for $15, as the included one is weak and heavy (although I used it for 5 months). If you go with a Sprint or Verizon phone, you will most likely be paying more for the phone.
For $30/month, Voicestream only offers you 200 anytime minutes (with no night minutes, only weekends) so I wouldn't recommend them.