Alternatively, you could just carry your clothes. I find a good compromise is to keep the shoes and belt in the office and carry clothes (they're not that heavy, and I already am carrying tools and lunch). Different strokes and all that. Oh, and I've done it either way regarding toiletries: carrying them if my office was far away from the shower, or just leaving them in the office if the office was close to it.

I really need to keep a set of clothing at work as chipcom suggests, though. It's really a good idea, whether you bike or not. What? You've never spilled something on yourself?