This is one of the best laid-back getaways in Vietnam. The town of Phan Thiet itself is a bustling little fishing port -- quite picturesque and good for a day's visit -- but you'll want to get out to the long, sprawling, sandy stretch of beach to the east: Mui Ne. This is a popular weekend getaway from nearby Saigon, and development in recent years has been rapid. You'll find some very nice upscale resorts and comfy little boutique bungalow properties.
Nick Faldo's golf course at the Novotel in Phan Thiet is a big draw, and the consistent winds of Mui Ne Bay bring windsurfers and kite surfers from all over the world. Farther east and north along the coast, there are vast sand dunes, like a beachside Sahara, and inland there's the famous and strangely verdant Silver Lake amid the towering, shifting sands -- a good day trip. These spots, as well as other small fishing villages, make for great day trips. There are also some local Cham ruins, and the town of Phan Thiet, famous for a brand of fish sauce (nuoc mam) made here, is worth exploring (especially the market). Phan Thiet is a good getaway from Saigon or a good place to take a break as you make your way down the coast.