I'm a graduating senior (in December, no I'm not graduating next week though I wish I was!) and I've got a list going but I'm still not sure how to evaluate master's programs. My field of interest is relatively niche, so I've been having a fairly hard time finding programs that might work.
I did two overlapping things while I was searching for PhD programs:
I remembered work that was in a similar vein to what I wanted to do, or that had impacted my scholarly development in a positive way. I then figured out where those scholars were. If they were in a top-level graduate program, I put them on the list. If they were on a lesser school or in a department without a PhD program (such as a liberal arts college), too bad, move on.
I looked at the top-20 or so programs and saw who was there and if I would be interested in working with them. The top tier will vary somewhat by field and subfield, but it will generally include most of the Ivies, several other great private schools (Stanford, Chicago, Duke), and the top public schools (both big UC schools, Michigan, UNC, UVA) (Note that this list is not intended to be comprehensive). In certain fields or subfields other schools will have high-quality programs. You can get a sense of their quality through rankings, kind of, but also by asking your professors, the placement rates and locations of recent PhD graduates, and their ability to fund PhD students fully.
This leads me to another source, one that I did not fully explore due to unique personal circumstances, but that you definitely should: Ask your current professors. They should know both you and their field well, and can steer you in a good direction. If you post more about your interests, some of the contributors here might be able to help, too.
Finally, you say you want a Master's rather than a PhD. Unless your family is wealthy and can pay for this degree out-of-pocket, I strongly urge you to minimize your debt any way you can. Paying for an MA in the humanities (as I did) is quite foolish, and can be financially crippling. Consider the flagship university in your state, or consider moving to a state for a year to establish residency before beginning your MA at THAT state's flagship. Another course is to get a job at the school you wish to attend, and then use your employee tuition remission to get your MA part-time over several years while earning a salary. In an MA specialization is somewhat less important than PhD, as is prestige, and you can go for higher levels of both specialization and prestige if you end up going on to a PhD.