There is, of course, Kahn Academy for fundamentals. We have already had a discussion on How to learn math.
What resources exist detailing which mathematics to learn in what order? What resources exist that explain the utility of different mathematical subfields for the purpose of directing studies?
My favorite professors are all rated 4.5 or higher, and my least favorites are rated 3.0 or lower; ones I'd rate in between are commonly rated higher than my favorites, but it contains substantially greater than 0 information relative to my school. Apparently YMMV!
I would guess talking to TAs or other same-major students is going to get most LWers a more useful perspective than RMP, but website reviews are still better than nothing.
Only detailed reviews. If you don't know what the criteria are, they can easily be worse - counting as negative a factor you would consider positive, for example.