Regardless to the state of the economy, one should always look for ways to save money and earn bonus points. I tend to use my rewards earning credit cards (Amazon Visa, Amex) to pay for as much goods per month (Gas, Grocery, Food, etc.) as allowed. When a statement issues at end of month, I'll pay off balance in full to avoid finance charges. This is a great way to earn rewards and bonus for your day to day goods. What I didn't realize is that telecos actually allow payments to be made with a credit card (and most brands are accepted, including AMEX). So yours truly decided to do a little research for you to see what your options are, information as accurate as of today, click on hyperlinks below for details (12/7/08):
AT&T accepts pretty much every card out there (Visa, MasterCard, American Express, Discover and Debit Cards w/ Visa or MasterCard logo). Everything can be setup conveniently online.
Verizon will also accepts Visa, MasterCard, Amex and Discover as well as debit cards. They even accept Diner's card (who still uses this?) for businesses.
Sprint accepts the same major cards as well, Visa, MasterCard, Amex, Discover and Diner's Club. A reference link here says Amex Hilton earns 5pts per dollar, but some argue their points are less value.
TMobile accepts Visa, MasterCard, Discover and Amex. No mention of debit cards but they do have a handy setup guide with screenshots for newbies.