I manage a network of four public NTP servers and would recommend to check your ntp.conf before going life.
Some Linux installations have by default stratum 1 servers in their configuration file (these are time servers directly synchronized by Cesium clocks etc). The stratum value tells you how many hops the time server is away from a physical clock. A stratum 1 server is the clock itself, stratum 2 servers are synchronized by a stratum 1 server, stratum 3 servers by a stratum 2 server etc.
Stratum 1 servers should be reserved for really time critical synchronization purposes like scientific research etc. Stratum 2 and stratum 3 servers still offer accuracies of the order 10 msec which is sufficient for almost all real-world applications. Connecting to a higher value stratum server prevents the central time servers from being overloaded and helps the accuracy of the NTP network in general. (To get an idea: my US based stratum 2 server serves on average 230 requests per second which is the equivalent of 1.9 gigabyte network traffic per day).
You can also connect to one of the pools of the NTP Pool project. More information of the available server pools for your region can be found on www.pool.ntp.org [pool.ntp.org].