HTTP Time Protocol is a time synchronization tool that uses Web server responses (HTTP headers) instead of the NTP protocol. If you are behind a corporate firewall, NAT device, or proxy server, HTP will still be able to synchronize the time. For high precision time synchronization, use ntpd.
chrony is a client and server for the Network Time Protocol (NTP). This program keeps your computer's clock accurate. It was specially designed to support systems with intermittent Internet connections, but it also works well in permanently connected environments. It can also use hardware reference clocks, the system real-time clock, or manual input as time references.
redWall is a bootable CD-ROM firewall which focuses on Web-based reporting of the firewall's status. It includes Snort, snortsam, dansguardian, and support for fwbuilder, squidguard, reporting (using BASE/sarg/ntop/webfwlog), VPN (Openswan/PoPToP/Openvpn), Spam Filtering (spamassassin, dcc, razor2, clamav, amavis-new, dspam and maia mailguard), and mail-based, alerting. Configuration data are stored on a floppy or USB disk.
linuxptp is an implementation of the Precision Time Protocol (PTP) according to IEEE standard 1588 for Linux. The dual design goals are to provide a robust implementation of the standard and to use the most relevant and modern Application Programming Interfaces (API) offered by the Linux kernel. Supporting legacy APIs and other platforms is not a goal.
OmniSync is a driver for NTPd for people who are firewall-challenged. It enables systems to synchronize time when port 123 (UDP) is blocked. It allows you to sync against the daytime service, time, SNTS, IRC, ICMP, SNMP, precision time protocol (PTP -- IEEE 1588), HTTP, HTTPS (both also via proxy server), and (S)NTP via a Socks(5) proxy server. It doesn't directly set the clock, but uses NTPd for this, as this enables you to have multiple time sources as well as bad-chimer detection, etc.
SNTS (Simple Network Time Sync) is a simple, fast, and low-overhead time syncronization system for LANs. It is designed as a simple replacement for timed with better time control and better portability (for systems without a standard adjtime() call, such as Linux). It uses broadcasts to negotiate servers and set time, and allows multiple groupings of servers on a network for independent time management for groups or labs. SNTS also supports multiple servers in a single group.
DOCSIS Server is a DHCP/TFTP/TOD/syslog server that uses MySQL as a backend. If you have a DOCSIS Cable Modem headend, you can use this server to boot up cable modems and assign IP addresses to customer premise equipment. With a little bit of tweaking you could also use it as just a DHCP server attached to a MySQL database. It was designed to boot up more than 150 modems per second.