time
gpio_ntp - sync a Linux system with NTP to the state of a GPIO pin (from userspace)
jans - NTP server that deliberately returns bogus time
omnisync - OmniSync is a driver for NTP for people who are firewall-challenged
ping-test - Test if calculating the Allan deviation of a ping-sweep works
timeweb - Show NTPSEC & GPSd statistics in a web-interface
pps-comparer - Measures the difference between PPS pulses