I carry stuffs daily in a vinyl messenger bag, regardless of the weather. The vinyl shields my books from elements. My belongs never get wet in the bag.
In winter, I install a pair of strap-on fenders. Pretty much that's it. I always let the bottom part of my jeans and shoes get wet. There aren't much that i can do. A pair of good quality rainpants are too pricey. Typically, my legs are soaked for 8 or 10 hours until I arrive home. Oh, I do wear a weather-proof jacket, though. In sub-zero weather, I even put on two jackets.

I'm used to getting wet in countryside.