Another handy resource is the FreeBSD Ports Monitoring System (also known as portsmon). This system comprises a database that processes information from several sources and allows its to be browsed via a web interface. Currently, the ports Problem Reports (PRs), the error logs from the build cluster, and individual files from the ports collection are used. In the future, this will be expanded to include the distfile survey, as well as other sources.
To get started, you can view all information about a particular port by using the Overview of One Port.
As of this writing, this is the only resource available that maps GNATS PR entries to portnames. (PR submitters do not always include the portname in their Synopsis, although we would prefer that they did.) So, portsmon is a good place to start if you want to find out whether an existing port has any PRs filed against it and/or any build errors; or, to find out if a new port that you may be thinking about creating has already been submitted.