As far as what I'm wearing, I've got some good clothes for cycling. There's a shower at work, so I don't have to worry about that (gym with a locker, so I've got clothing stuff covered).
I do need to get a spare intertube (or 9), especially since I've read that the stock Specialized Mondo tires on my bike don't hold up so well to rough city roads (granted I have a pretty straight shot down Milwaukee and that's a pretty nice road). I've heard good things both about Specialized Armadillo tires and continental gator skin tires. Any recommendations for flat prevention? I'll have to invest in that second U-lock, and that link to Sheldon Brown's site was quite helpful (come across his stuff before).
Are you guys fans of hand signals when turning?