I'm thinking of switching over to the "smart talk" plan dukalmighty is talking about from Walmart. We have 4 people at work who has switched over to that plan and love it.
You can keep your current phone and current phone number (in most instances). They just issue you a new Sim card.
Unlimited voice/text/data for flat rate of $45/month per phone. So for my wife and I, it would be $90/month.
I had to drop my data plan last year because it was getting to be just too expensive. Right now, with no data on either of our phones, and paying for a limit of 200 texts/month (on my phone only) we are paying about $130/month for the two lines with all the hidden taxes.