NTP official reference implementation (for Unix and Unix-like OSes, with ports to Microsoft Windows NT, VMS, real-time OSes like VxWorks and QNX). Also jumping-off point to the official NTP documentation and FAQ, community documentation tools (twiki), poo http://www.ntp.org/
NTP Project page for Dr. Mills, primary NTP researcher for over twenty years. He and his students are working on NTP version 4 to improve robustness and security. http://www.eecis.udel.edu/~mills/ntp.html
Community maintained list of public Stratum 1 and Stratum 2 NTP time servers, including policies and requirements for use, contact information. Maintained via the NTP TWiki, by the admins of the respective sites themselves. http://ntp.isc.org/bin/view/Servers/WebHome
Not the official NTP documentation or the official NTP FAQ. Intended to be the collection point for cookbook configurations, tips, hints, tricks, and other comments from directly from various members of the NTP community that might be beneficial to others http://ntp.isc.org/bin/view/Support/WebHome
Report by Dave Plonka on the massive problems caused on the University of Wisconsin network and time servers, due to misconfiguration of NetGear equipment http://www.cs.wisc.edu/~plonka/netgear-sntp/
The current standard for SNTP, a version of the protocol for implementations which do not need all of the features of NTP. Available here in HTML, PDF, and Postscript formats. http://www.faqs.org/rfcs/rfc2030.html
This is Part 2 of a three-article series that discusses how to use Network Time Protocol (NTP) to synchronize system clocks. This article explains the basics of client and server administration, covering various client/server configurations, as well as au http://www.sun.com/blueprints/0801/NTPpt2.pdf