I used to be a huge fan of just wearing whatever street clothes I would normally wear on my short commutes. With jeans, however, it gets uncomfortable for me after only a few miles.
Lately, I've worn a wicking shirt and shorts with mesh inside whenever I've got to get across town. Nothing fancy. Certainly nothing that makes me look like a serious cyclist. It's cooler. It's really visible. My legs get some sun. Otherwise, I'd have legs as white as my old man.
I'm thinking of investing in a decent pair of sunglasses, though.