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/
Power Domain Name Server - PowerDNS is a non-BIND nameserver based on open-source and proprietary software. - http://wiki.powerdns.com/
.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
MyDNS - A free DNS server for Unix that serves records directly from a MySQL database. - http://mydns.bboy.net/
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/
Life with djbdns - Examples and howtos for djbdns. - http://www.lifewithdjbdns.com/
MetaInfo - DNS and DHCP server software for MS Windows, Linux, and Solaris. - http://www.metainfo.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/
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
ZoneMaster - Open source project manages nameservers and zonefiles. Free download, development status, screenshot. [Perl, PHP source] - http://www.zonemaster.org/
Simple DNS Plus - Free trial version, screenshots, client testimonials, FAQ, tutorials. Also provides a Web-based DNS lookup tool.[Windows] - http://www.jhsoft.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/
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
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/