It depends. Most hiring gurus say you should not ask about salary during a first interview because doing so makes you look like you are just interested in the money and not the job itself. An article I read on one of those job sites said you appear "greedy even if you aren't." Another article I read said that you could knock yourself out early by asking about salary in the 1st interview. Some hiring managers say that even if you are just interested in the money, don't knock yourself out by asking about it too soon.
In many job interviews, the interviewer will hand you a copy of the job description, which usually includes salary info. If you see a salary listed on anything they give you, or if there was a salary listed, say in a newspaper or online ad, it is ok to ask something like, "Your advertisement indicated that the salary is $xxx. Is that the salary I would start out at?" But wait until the end of the interview when you are asked "Do you have any questions?"
If you are called back for a second interview, then discussing salary is acceptable, because you have advanced in the hiring process. But again, don't ask right at the beginning.