Which Cambridge colleges have the best mental health support?

All Colleges have access to the uni's central counselling system, which is pretty good. Some colleges will offer additional support - through their own teams of counsellors or funding available (usually only if the university or NHS won't see you, or special requirements etc.). As far as I know this information isn't compiled anywhere, and for a lot of colleges the webpages detailing this are only available to members, unfortunately.

In addition to counselling, colleges have different approaches to mental health - how lenient will they be with deadlines, grades etc.. There's no official policies or anything on this one, so probably your best bet is contacting students at the college or the JCR.

In general, though, colleges will be pretty much the same for this, since so much of it is run centrally by the uni.