You can get free cell phones from most companies, as long as you sign a contract. The only thing with most of those is, they're your most basic phones. This is the option I chose and I'm pretty happy with it. After I believe 1 year, I get $150 credit towards a new phone. I chose Cingular here in Dallas. Actually at the time it was Southwestern Bell, but they had some of the best coverage for this area. Nationwide their coverage is limited. Will you be doing any travelling? If so, you might want to consider Sprint. While their local coverage isn't as good, their overall nationwide coverage is probably one of the best.
If you really want a GOOD phone look to spend $199. That's going to get you a phone with most of the bells and whistles, vibrate, ability to download ring tones into it, play games, probably come with a handsfree kit and car charger, as well as a home charger. Of course getting a nicer phone, also generally means less time is needed to charge it because its battery life is better than the less expensive phones. I personally just didn't want to spend a lot on the phone so I went with the free one.
As far as how long? If you go to a store you could walk out with an activated phone if you wanted. I just called a rep over the phone, he overnighted me the phone, and the next day I was in business but it's really up to you. If you have the time to go shopping at a Cingular store or a Sprint PCS location (they're in all the radio shacks too) then I'd do that.
dm