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.
dnscrypt-proxy acts as a DNS proxy between a regular client, like a DNS cache or an operating system stub resolver, and a DNSCrypt-aware resolver, like OpenDNS. The DNSCrypt protocol focuses on securing communications between a client and its first-level resolver. While not providing end-to-end security, it protects the local network (which is often the weakest link in the chain) against man-in-the-middle attacks. It also provides some confidentiality to DNS queries.
Chaosmap is an information gathering tool and DNS, Whois, and Web server scanner. It can be used to look up DNS names with a dictionary with or without using a salt. Salting for DNS means it will append numbers from 1-9 to the name in the dictionary with or without a - and _ or a leading 0. Salting for Web stuff will try double slashes and some directory traversal tricks. It performs reverse DNS lookups of a whole IP range (with optional Whois lookup) and dictionary scans for hidden paths on one Web server or a range of IP addresses. Optionally you can encode a path with URL encoding use Google dict lookup mode to find the path on Google and only query the Webserver if there are no search results. It can also extract email addresses from domains using a Google search or perform a list of Google Hacking queries on your domain.
adsuck is a small DNS server that spoofs blacklisted addresses and forwards all other queries. The idea is to be able to prevent connections to undesirable sites such as ad servers, crawlers, etc. It can be used locally, for the road warrior, or on the network perimeter in order to protect local machines from malicious sites.
OpenDD is a DynDNS client, written in C, and especially designed for small gateway machines, like a Soekris box. Its main feature is that it does not require any Perl or Python interpreter. It supports HTTPS, can send a mail report, and can run as daemon. It is also very easy to deploy.
NicTool is a DNS management suite with support for various DNS servers (djbdns, BIND, PowerDNS), SQL data storage, DNS entry parsing (RFC 1034 & 1035 compliance), tiered and delegated permissions so you can safely grant access to clients and admins, giving them only the permissions they need. Humans interact via the Web interface, and an API is used for scripting mass updates, DNS templates, provisioning, and more. All changes are logged to easily track change history and see who changed what, and when.