You could use find, but it is easier to use the built in facilities to search for ports. If you are in the ports directory you can:
make search name=name_of_port
to search for a port by name and:
make search key=key_to_search_for
to search by key. You can also use quicksearch instead of search to reduce the verbosity of the results. If you read the ports man page, you will find a bunch of other nifty things you can do with the ports system.
FreeBSD also has a binary package management system, see http://www.freebsd.org/doc/en/books/handbook/packages-using..... The ports take precedence, though, in that they can have newer versions and not all packages on all architectures may be available as binaries.