Beagle Software - Software and hardware to keep computer clock synchronized to the Atomic Clock over the Internet. - http://www.beaglesoft.com/
Chrony - A Unix-based NTP implementation specifically written to be suitable for computers with dial-up connections to the Internet. - http://chrony.sunsite.dk/
FACTS - A freeware GUI-based SNTP client for the Amiga, which will synchronize system time to a server across the Internet. It is also capable of automatically switching in and out of DST. - http://www.unsatisfactorysoftware.co.uk/facts/
Network Time Protocol (NTP) Project - Links to many time service clients from the maintainer of the NTP. Includes non-NTP clients. - http://www.ntp.org/
AnalogX - Atomic Time Sync - Queries the NIST NTP server to set the computer clock to the exact time. - http://www.analogx.com/contents/download/network/ats.htm
AtomSync - A background utility that periodically checks a PCs clock against an internet NTP time server or against a computer in a LAN (local network) which runs an AtomSync LAN time server. - http://www.emtec.com/atomsync/index.html
Sync-It with Atom - Network Time Protocol client for Windows with a nice user interface. - http://www.tolvanen.com/syncit/
Klox - Windows 9x/NT freeware decorative desktop clock, with different faces and Internet time server syncronization. - http://www.klox.com
TymServ - Time reference that draws from multiple time sources. Computer networks and systems can be automatically synchronized. - http://www.tymserve.com/
WorldClock - Allows the user to synchronize his or her PC to Internet time servers. Supports both the Time or SNTP protocols. Also provides timezone, alarm and calendar features. - http://www.carefile.com/WorldClock
Clocks and Time: Time Software for PCs - Lists PC based software for time setting and synchronization, clock rate correction and time display. - http://www.ubr.com/clocks/timesw/timesw.html
CHU Time Synchronization for Linux - Software to synchronize a Linux system to the Canadian CHU shortwave station. - http://www.rossi.com/chu/
Java Clock Applet - Supports network synchronization via SNTP, HTTP, Time, and Daytime protocols. Free download. - http://www.rossi.com/java/7seg2.html