I'm pretty sure multivariable calculus questions can be easily answered in the this general calculus page.
As for linear algebra, I'd say your best bet is to try the Precalculus section. In my experience, there is an overlap between Precalc and some Linear Algebra material (systems of equations, vectors, projections, etc.), so until socratic adds in a Linear Algebra-specific section, that'd be your best bet.
Also, for the future, logistical questions like this would be best posted in the Socratic Meta Section! :)