nope, but it is might only be available in certain areas of the country. About a month ago I wasn't able to check my minutes (under manage my account), but now I can. Go to
this page to setup an account and try checking it.
gwalm12: you can change your plan at any time, just call them up. With certain promotional plans, you might have to extend your contract, but this is not usually the case. I've switched rate plans 3x without penalty - although be aware that they either prorate the minutes your first month or wait until your next billing period to activate it.
Cingular is fantastic here in Dallas.