There are still comfortable options like ballet flats, fashion sneakers, or even simple leather sandals that still look somewhat professional.
Here are a few examples of super cute, yet wear-to-work appropriate flats and sandals from Anthropologie.com:



And an example of a simple and sleek fashion sneaker by Camper, courtesy of Endless.com:

I meant to post this at the start of summer, but alas, studying for the bar exam got the better of me and I forced to delay this bit of shoe advice. But now that the bar exam is behind me (I hope!), and September is upon us, take this bit of advice and keep the flip flops away from the office. There will be warm days to come, but resist the temptation - back away from the flip flops on weekday mornings.