Time

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

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/

CHU Time Synchronization for Linux
Software to synchronize a Linux system to the Canadian CHU shortwave station.
http://www.rossi.com/chu/

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

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/

Java Clock Applet
Supports network synchronization via SNTP, HTTP, Time, and Daytime protocols. Free download.
http://www.rossi.com/java/7seg2.html

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/

Sync-It with Atom
Network Time Protocol client for Windows with a nice user interface.
http://www.tolvanen.com/syncit/

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