Starting July 1, you'll be able to get all the minutes you want for $79.99/month thanks to Virgin Mobile. The "Totally Unlimited" plan will work nationwide with no contract necessary. You'll be able to pay via cash or credit, and you're not going to get hit with roaming charges, which is a big advantage over similarly priced regional offerings.
Another $10 each month will get you unlimited SMS/MMS/Email/IM messaging on top of all of those minutes. Looks like a pretty good deal for anyone who makes it a personal practice to avoid contractual agreements like the plague.