I just bought a Trek PDX and plan to start commuting to and from work (2.5 miles each way) and around town. I have a question for the experienced commuters here - what sort of cycling gear do you recommend? I am looking for a backpack to carry my work clothes and books and would preferably like a waterproof one as I plan on riding year round. Any good suggestions? The only brand I have found so far that I have liked is Timbuk2. Also looking for clothing suggestions.