EndRun Technologies - Provider of time and frequency equipment including NTP Servers.
Galleon Systems - Provider of NTP time synchronisation solutions using the MSF radio signal and GPS satellites.
Meinberg USA - Manufacturer of hardware Network Time Servers (NTP) for IPv4 and IPv6 networks.
Network Time Protocol (NTP) Project. - The official page for the NTP Project. Contains information about the project, reference implementations of the protocol and software links. Also links to the pool of public NTP servers.
NIST Web Clock - Shows the official US time in each time zone.
Open NTPD - A mainly BSD implementation of the Network Time Protocol.
PresenTense Time Server - Windows time server which synchronizes itself with any true time source, including GPS via rs-232 com ports and then acts as a time server for all network clients. Screen-shots, features list, documentation, and free 30-day demo version.
TimeTools - Specializes in computer and network timing solutions. Using NTP for network time synchronisation in conjunction with MSF, DCF-77 and GPS time sources.