Address Management

Adonis DNS Management Server
Plug-and-play 1u rack-mount GNU/Linux server hardware with BIND pre-installed.
http://www.bluecatnetworks.com/products/adonis-dns-dhcp-appliances/

Chami.com: WhoIsNot
Finds reserved, on-hold and available variations of domain names. Detailed list of features, free trial version, FAQ. [Windows]
http://www.chami.com/whoisnot/

Cisco: Network Registrar
A scalable DNS server. Free trial version, FAQ, technical documentation. [Windows]
http://www.cisco.com/en/US/products/sw/netmgtsw/ps1982/index.html

Djbdns
Domain Name System tools, links, and tips. [Unix]
http://cr.yp.to/djbdns.html

DNS Boss
Management software for Solaris, NT, Linux. Free trial version, documentation and instruction.
http://www.dnsboss.com/

Internet Software Consortium
Non-profit corporation dedicated to developing and maintaining production quality open source reference implementations of core Internet protocols. BIND is available here for free.
http://www.isc.org/

ISC's BIND
The developer's site for the Berkeley Internet Name Daemon at the Internet Software Consortium.
http://www.isc.org/sw/bind/

Life with djbdns
Examples and howtos for djbdns.
http://www.lifewithdjbdns.com/

Linux NIS(YP) Server and Tools
The Network Information Service (NIS) provides a simple network lookup service consisting of databases and processes. It was formerly known as Sun Yellow Pages (YP).
http://www.linux-nis.org/nis/

The Manual Page: DHCP-DNS
Free Perl package that allows dynamic DNS update using your DHCP server. GPL license. News, and a glossary of relevant technical terms.
http://www.themanualpage.org/dhcp-dns/

MaraDNS
A public-domain, open source Domain Name Server which offers both authoritative and caching features. Its main goals are security and simplicity.
http://www.maradns.org/

Men & Mice
QuickDNS and DNS Expert tools. Free trial versions, support page including DNS glossary, FAQ, mailing list. [MacOS, Windows]
http://www.menandmice.com/index.html

MetaInfo
DNS and DHCP server software for MS Windows, Linux, and Solaris.
http://www.metainfo.com/

MyDNS
A free DNS server for Unix that serves records directly from a MySQL database.
http://mydns.bboy.net/

.Net API wrapper for Simple DNS Plus Windows nameserver
A free .net wrapper for users of Simple DNS Plus, using the built-in HTTP API of Simple DNS Plus.
http://www.neokobe.nl/free-net-api---windows-dns-nameserver---simple-dns-plus.php

Power Domain Name Server
PowerDNS is a non-BIND nameserver based on open-source and proprietary software.
http://wiki.powerdns.com/

Sauron
A free GPL licensed DNS and DHCP management system. Includes a detailed presentation, screenshots and documentation.
http://sauron.jyu.fi/

Simple DNS Plus
Free trial version, screenshots, client testimonials, FAQ, tutorials. Also provides a Web-based DNS lookup tool.[Windows]
http://www.jhsoft.com/

Unbound
A validating, recursive, and caching DNS server software product distributed in open source form under the BSD license. [Unix]
http://www.unbound.net/