I don't know how popular it is to have one of these programs outside China, but here behind the Great Fire Wall, it's essential if you want to read the New York Times, get on Facebook or Youtube, Tweet or access any number of other websites. China is increasingly clamping down and censoring more and more sites, if you're outside China, you can read about it in this NYT article; but if you're on the mainland, you'll need a VPN to access it.
Frustrating as it is, many of us get around the Fire Wall with use of a VPN - a program that allows internet users to access websites blocked in China. Depending on the service provider, there are subscription charges for VPN use and you need to specify if you'll be using it on a laptop, smartphone or tablet (or all three, there are various packages).
If you're only coming to China for a few days or a few weeks, then it's probably not necessary for you to go to the expense. But if you'll be here on extended travel or work, you might consider it. If you do decide to get one for travel to China, be sure to tell the service provider where you'll be using it as there may be certain settings depending on your location.
Read more from my colleague at Computing/Networking: