Nha Trang: Vietnam's Ocean City is very crowded in the summertime with domestic tourists, but it's a great escape. The city has a few worthy sights -- otherwise a cluttered market town -- but there are some great new resorts and the best seafood going.
Mui Ne Beach, Phan Thiet: Just a few hours from Saigon, Phan Thiet is the latest getaway for Saigon expats. There's a golf course designed by Nick Faldo, the seafood is good, and there are some great day trips to remote sand dunes and smaller fishing villages.
Phu Quoc Island: Phu Quoc boasts vast tracts of interior forestland and far-flung beaches great for exploring by motorbike. For now there's just a small clutch of mid- to low-end resorts, but the times they are a-changin' and development is on the way. Get here fast.