Unlike the question about salary history, the question about salary expectations remains legitimate. How to handle it depends on the point in time in the application and interviewing process (such as: when you first apply; during a phone screen; an in-person interview; or the job offer). But one thing is certain:
You want to show the employer you know what you are worth.
For online research, websites such as Salary.com and Indeed have reportedly been helpful. Then there is O*NET OnLine, where you can review all conceivable aspects of just about any occupation, including wage info by state.
Since I live and work in Massachusetts, let me point to MassCIS, which I find a very helpful online tool. When you review a given occupation, MassCIS at first gives you an at-a-glance view with just one figure for salary info, as seen in the screenshot below.
Like O*NET OnLine, MassCIS uses wage information provided by the U.S. Bureau of Labor Statistics. So if you can’t find the equivalent of MassCIS in your state (pardon me for not knowing), and you don’t mind a few extra clicks, you can always try going directly to the U.S. Bureau of Labor Statistics website.
Online research is just one avenue of research, of course.
Help from people who can connect you to inside information is invaluable. Getting information from a variety of sources will allow you to take miscellaneous factors into account when preparing for an employer’s salary-expectation question. And with that, you will be more likely to make a compelling case.