Introduction: I'm a freshman math major at MIT who might know what it is you want to learn, or else can perhaps try to learn it and then teach it.
I have some experience tutoring, and lots more experience helping people with homework, back in the high school days.
Things I can help with include, but are certainly not restricted to:
Everything up to calculus, multivariable, linear algebra, differential equations
Introductory real analysis, abstract algebra, and some other topics
High school contest math (I made the USAMO three times and won various contests)
Classical mechanics, E&M, and quantum mechanics
Introductory microeconomics or computer science. algorithms and complexity
and other stuff
I'm going to say $15 an hour for now, but I might ask for more, or go for less (especially if the student is actually interested and motivated to study the subject).