There is some very helpful Vector Analysis (and Multivariable Calculus as a whole) supplementary material at http://www.math.umn.edu/~nykamp/m237...gs/#vectorcalc
. These informal "readings" contain some very instructive interactive 3D graphics animations utilizing "LiveGraphics3D" Java applets. [A java enabled browser is therefor required]. The various presentations provide the ability to interactively explore, in fully rotatable 3D, such important concepts as line integrals and surface integrals with scalar and vector fields, the ideas behind Green's and Stokes' Theorems, the div, grad, & curl, etc. [Very nice presentation of curl]. It's amazing how playing with these visuals and reading the brief (but well chosen) explanations are able to produce fairly vivid long-term memories of ideas that seemed to otherwise tend to blur with time.