http://www.creativecow.net is a great place for video related tutorials. If you have adobe after effects, http://www.ayatoweb.com is another site which has a number of effects tutorials, geared toward the field of "motion graphics". Motion graphics are flashy effects based clips designed to stand out on the screen (like in advertisements, web banners and logos). This is opposed to film graphics effects which are designed to blend in to the existing footage (think harry potter, the matrix, anything with gun shots or explosions with people in them, etc).