To answer the second part of your question ... when I shot film, I carried a lot of color correction and special effects filters. Since my switch to digital, I only carry two filters -- my polarizing filter (which is great for those deep blue outdoor skys; and a pair of neutral density filters (half and full). I sometimes use my polarizing or ND filter in my studio when I want to shoot at a wider aperture for shallow DOF.
Here's a shot I took in Banff with a polarizing filter --
