My summer hat pick? The San Diego Hat Company's Ribbon Crusher hat. Made from grosgrain ribbon, it has a UPF 50+ rating, folds flat for packing, and is extremely attractive to boot. Available in 6 colors (Black/White, Brown/Pink, Brown/Teal, Navy/White, Red/White). I bought one last week and wear it everywhere- from commuting to weddings.
PS: Their fall catalog is available here.