The answer depends on who invites you to the interview.
If a headhunter or agency sets up the interview, they will usually tell me the salary range. If they don't volunteer that information, then I will ask them about the range.
If I am contacted directly by a company, it is usually in response to a position that I have applied for on their career site. If the salary is not posted in the job description then I refer to salary.com for additional information. The website typically has reviews by former employees, salaries paid for specific jobs, and may also have job postings.
Typically during the interview, the hiring manager will bring up the issue of salary. You should never, ever ask. However, you should know your worth based on experience, and you should be prepared to negotiate.