Keep some bike clothes at work, or if you can hang up your wet clothes to prepare for the ride home. I like the Kool Stop mountian break pads for wet weather. Save the bike shoes for normal weather, unless you want to spend money on oversized shoes and wear several pairs of socks, booties ect. I am about to change to platform pedals and boots, my toes are cold and it is a pain layering the feet. People here also reccomend layering the core, seems to work. Backlavas are great!
Good Luck