One resource we have used is Rate My Professor (
https://www.ratemyprofessors.com/ ). We found quite a bit of very good information about classes and instructors there...with one caveat.
The caveat is that DD has not actually
taken any classes from any of the people we researched, so we have no real way of knowing how accurate the ratings were. That said, we got the idea here on the DIS and people recommending it had good things to say.
You need to be careful about that site, especially if there are not a lot of ratings for a particular class/prof. When i was a post-doc I taught a second-year undergrad course in our my department for a few years. At the end of the course, we gave out feedback sheets, which the students filled out (anonymously), which i took very seriously (and adapted the course to improve it). The last year I was teaching it, one of the comments was something like: "This course was fantastic, I like how much you connected with us, etc.. I was really nervous to take the course after seeing the 1.0/5 rating on rate my professor, but I don't know what they were talking about!" At the time I had never heard of it, and so I went and looked it up. I had 2 ratings, from the prior year, both 1.0/5.0, complaining about how horrible a person I was, how the class was useless, etc. I recognized the writing style of one of the students, and from that figured out who the other student was.
In the prior year, I found out that two students who were roommates, had been cheating on assignments and take-home exams all semester long. When I confronted them about it, essentially allowing them to take a lower grade, but needing to re-do new assignments/tests, they became extremely belligerent, and challenged me: "and what are you going to do about it?" Well, both students ended up in front of the university's ethics committee, were failed in my course, and were suspended for a semester. It was also discovered that they had been cheating in other courses they took together. It was a really nasty situation. When I contacted that site about it, their response was "We don't take down student comments," and at least at the time, there was no way for me to even respond to the comments. Word got out, and my profile was swarmed with positive comments. I just did a search for my name, and I don't come up any more. Maybe they purge old profs/courses who haven't had any activity in a decade (or maybe I was mistaken and it was a different, though similar site). Just be aware, that any anonymous ratings site like that, can be gamed either way.