This work has been inspired by Sander Temme's and Sebastien Estienne's mod_zeroconf module, but supersedes it in every way. MacOSX ships with mod_rendezvous/mod_bonjour, but mod_dnssd is much more powerful than this piece of software as well. In short: mod_dnssd is definitely the greatest way to add Zeroconf support to Apache available today.
A few examples just to show how great mod_dnssd is:
This is everything you need to enable DNS-SD support in Apache after loading the module. It will publish all virtual hosts and all existing mod_userdir directories (i.e. ~/public_html) as services of type _http._tcp.
In case you want to publish some subdirectory of the web server as service, just place DNSSDServiceName inside a <Location> section for that path:
<Location /foobar> DNSSDServiceName "A special service called foobar" </Location>
You can even use it to publish WebDAV shares using Apache's mod_dav module:
<Location /webdav> Dav On DNSSDServiceName "A WebDAV folder" DNSSDServiceTypes _webdav._tcp </Location>
This especially cool since we now have a free software server counterpart for Gnome's and KDE's WebDAV client functionality.
Or to publish your blog as RSS service:
<Location /blog.cgi?rss> DNSSDServiceName "The blog" DNSSDServiceTypes _rss._tcp </Location>