slapi-dnsnotify is a plugin for OpenLDAP or other LDAP servers. It watches for changes in the serial number of a DNS zone stored in the LDAP server, and notifies DNS slave servers to refresh their copy of the zone. It can also increment the serial number of a zone whenever changes in that zone are made.
jresolver is a lightweight domain name resolver library written in pure Java. It is what RFC1034 describes as a stub resolver, i.e. it uses a single nameserver to do the hard work of resolving its queries. It operates using UDP as a transport, and has support for multithreaded querying and a robust resend and timeout mechanism.
Valtz is a simple tool that can be used for validating and filtering tinydns-data (djbdns) zonefiles. It can be used both as an error-finding tool by end users and by automated scripts to filter out errors. Additionally, it can be used to filter out domain-specific data that does not belong in a given file. Thus, importing zone information from third parties, semi-trusted parties, and sloppy users can be done without fear.
cqueues is a comprehensive event and networking library for Lua 5.2 and LuaJIT using modern Unix O(1) polling facilities. It includes libraries for buffered socket I/O, SSL/TLS sockets, DNS querying, signal handling, threading, file change notification, and X.509 key management. It natively supports Linux, *BSD, OS X, and Solaris systems without third-party dependencies, and is interoperable with any event loop that accepts plain descriptors, or is usable standalone.
mDNS Responder with Unicast runs on a server anywhere in a network and responds to mDNS queries across the network by performing a unicast DNS lookup and returning the result. Many networks use a .local top-level domain for their intranet. This has proven to be quite problematic as operating systems such as OS X have begun handling .local domains differently (in particular, prioritizing multicast DNS over conventional unicast DNS). Ideally, you'd have no problems moving away from a .local domain name, or simply not using one in the first place. That's not always possible, though. So with this tool, a lookup for "host.local" will be resolved via your existing unicast DNS servers, even if "host" does not have its own mDNS responder. Of course, the tool isn't limited to just .local domains, and can realistically work on any network where mDNS is in use.
Open Domain Server Update Client is a client in C, intended for Unix users, and will update your DNS records on the ODS server (http://www.ods.org/) with your new IP. A reborn dynamic DNS provider, ODS used to exist as the second largest dynamic DNS provider. After some downtime, it is now back up with 13 domains to choose from. The service is free.