Yes, login to AT&T online and it will show your minutes. The bad thing is that AT&T shows my minutes will expire on December 31. I guess that's the same with everyone since I didn't have AT&T till I got the iPhone.
I have iver 1500 rollover minutes that I will never use. 2008 will be a full year and I hate to see how many rollover minutes that I won't use at the end of 2008.
Edit: It says 0 rollover minutes will expire on 1/1/08 so I guess they won't expire but I still won't be using my rollover minutes ever.