At the risk of making my blog contain an even higher than usual number of complaints about things, I always get really annoyed when online payment forms show you a list of credit card expiration months using the name of the month. Sure, I know that June is 06, but the card says 06. Why would you show "June" in the dropdown box? That just doesn't make sense. It's okay to say "06 - June," but just showing "June" is silly.
At least it's not August. July and August are the ones I always have to count out; 07 and 08 never just come to mind for some reason.