.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/dns/simple-dns-plus-free-dot-net-api.php

Adonis DNS Management Server
   plug-and-play 1u rack-mount 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/

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

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

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/

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/

MaraDNS
   A public-domain, open source Domain Name Server which offers both authoritive 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/

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

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

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/

ZoneMaster
   Open source project manages nameservers and zonefiles. Free download, development status, screenshot. [Perl, PHP source]
   http://www.zonemaster.org/