Vicomsoft DHCP Server - A commercial DHCP implementation by Vicomsoft. Works on both Windows and Macintosh servers. - http://www.vicomsoft.com/products/netcomms/dhcp/
ISC - DHCP - Internet Software Consortium DHCP Distribution, mostly for Linux/Unix. Contains useful information for DHCP programmers and system administrators. - http://www.isc.org/sw/dhcp/
Anemon Dhcp - Server, client, and relay implementations written in python and SQL, with a web configuration interface. - http://anemon.org/wiki/
Incognito Software - IP Commander - A multi-platform commercial DHCP implementation, also available as an appliance. - http://www.incognito.com/products/IPCommander/overview.jsp
ipLease DHCP Server for Windows - Server for Windows systems. A commercial product with a free trial period. - http://www.billiter.com/
FutureDHCP - Portable implementation of the Server and Relay Agent components as specified in RFC 2131 and RFC 2132. - http://www.futsoft.com/dhcpra.htm
Microsoft DHCP Basics - A basic technical page covering the Microsoft implementation of DHCP client, server and relay-agent, over different MS-Windows versions. - http://support.microsoft.com/default.aspx?scid=kb;EN-US;q169289
LinuxPlanet Tutorial for ISC-DHCP - A short and basic tutorial for ISC-DHCP for new system administrators. - http://www.linuxplanet.com/linuxplanet/tutorials/894/1/
Microsoft Release Notes for Windows NT 4.0 Service Pack 4 - A list of articles from Microsoft about issues with DHCP (as well as DNS and WINS) over Windows NT Server. Useful for problem solving. - http://support.microsoft.com/default.aspx?scid=kb;EN-US;q184693
DNS One - A commercial DHCP and DNS Server integrated in one box. a product of InfoBlox, Inc. - http://www.infoblox.com/
Freshmeat.net DHCP Page - A catalog of DHCP and DHCP related software for Unix, Linux and cross-platform open-source. - http://freshmeat.net/search/?q=DHCP