I can actually speak from experience on this since I am in the process of getting a cell phone myself and have been doing lots of research!
Two great sites I recommend are
http://www.clarkhoward.com Clark Howard is this consumer advocate guy and has good cell phone info on his site. Also
http://www.point.com (click consumer, not business) is a great way to compare plans through many different carriers and you can chose different options you want based on your needs.
There are a lot of $20-ish plans out there but for $10 extra bucks the $30 plans are a lot better. Word of advice, I'd stay away from Verizon Wireless. Many DOD members have had bad experiences with them. I've started a thread about that while back so you might want to use the 'search' feature in the top right hand corner and type in 'verizon' or 'cingular' or 'powertel' or 'cell phones', etc....
I live in Athens, GA and I have narrowed it down to either Powertel or Cingular depending if me and my boyfriend keep our landline (lingo for the regular phone in the house) Cingular is doing a great 29.99 promo called Cingular Home 250 that gives you 250 minutes, free LD (long distance), and a choice of either rollover minutes OR 1000 free nites and weekend minutes (their nites begin at 8pm and end at 7a, and weekends begin Fri at 8pm and end Mon at 7am) Pretty good deal. Plus for an extra $14.99 you can get a second line added to that account that will share the 250 minutes only maybe the free LD but only the 29.99 phone number gets the promo roll over or free nites and weekends.
Powertel has a good plan for $20 I think called Powertel Weekend 20 Promo or something. And you get 100 anytime minutes and 1000 weekend minutes. Powertel is also running a promo where if you sign up with them you get a $50 credit on your 2nd phone bill - even if you sign up for their cheapie plans! Powertel only uses single band phones which Best Buy told me will probably end up being phased out in a couple of years cuz dual band is betting and helps when you travel. Powertel includes free voice mail and caller ID which Cingular does not.
Also through my research I've realized that AT&T wireless does not have competitive prices and does not offer as many free perky stuff. Although I don't recommend Verizon they have a $20 plan called Digital 50 and you get 50 peak minutes (7a-7p) and 450 off peak minutes. Radio Shack is doing a promo where you get an instant $25 instore credit when you sign with Verizon to apply toward a phone and they had a 29.95 Motorola phone that ends up only being $7-ish including tax. But again, lots of DOD members do not recommend Verizon.
Well I hope this lengthy e-mail helps. Let me know what you decide!!!!