I commute to work/school but ferry, via car, my clothes once a week to the locker room where I change/shower. On the bike I carry books/research in a backpack. I found that carrying the amount of books and paper that I need in a messenger bag caused me back to hurt.
As for rain...well, I live in Tucson, so I don't see much of it. During the monsoon season (June to August, roughly) I'll occasionally get caught in a monsoonal downpour, but to be honest, it's a nice way to cool off....so I don't carry raingear, then. During the cooler months, December to Marchish, I'll wear leg warmers and a thin microfiber jacket, with maybe a long sleeve jersey underneath or a short sleeved jersey w/ arm warmers. In any case, I'm comfortable in the coldest temps we get--low 30's, occasionally high 20's--with that setup.
Part of my commute is usually in the dark. I use a Cygolite w/ dual bulbs mounted on my helmet and powered by a huge, clunky battery. What I'd like to see is a helmet mount light with a high capacity battery built in that recharges quickly and is uber bright. None of the LED lights I've seen on the road come close to my light for brightness. In any case, it'd be nice to be rid of the cable running from my helmet to the battery in my backpack. Helmet mount is essential since I think it improves my visibility to cars: I can look right at them, and the light better insures that they'll see me.
As for biodegradeable stuff, I'd like to see more work on bio-friendly cleaners, degreasers, lubes, oils and the like, but outside of those things, there's really nothing else that needs to be bio-friendly.
Outside of that stuff, I'm pretty chuffed with the state of the art of the bike kit that I have, from components to clothes.