Switching cell phone companies and keeping your phone number:

Update 11/20/03: I finally decided to take advantage of the seemingly good deals that abound on the web lately for free or heavily discounted phones with new service agreements. I opted for ATT GSM service and a 2 year contract after considering TMobile and Verizon. I found that the ATT rate plans for "national family" plans were much more competitive than the TMobile plans. TMobile's low end shared minute plan was $60, where with ATT I got a good plan with plenty of anytime and mobile to mobile minutes for $49.99 month. I purchased two nokia 6200 phones which were the best phones I could find with good reviews, not too many features like cameras and video recorders, cheap. The TMobile 6610 phone is similar to the 6200. I ordered directly from the attwireless web site and got a good shared plan with 550 anytime shared, 1000 anytime mobile 2 mobile, national plan, free long distance, free car charger, no activation fee, $100 rebate, and a few other things. The plan allows us to have 2 phones and one bill.

More information on transferring your existing number: HERE

I plan to do this from Sprint to Verizon. Should be an interesting experience. I would try to exploit Sprint to get a better deal, but I'm so tired of their substandard signal quality that I don't care what deal they might cut at this point.
Yahoo! News - How to Exploit the New Cell-Phone Rules