Running postgresql in Mac Terminal
Try specifying -h localhost as a psql parameter, to connect via tcp/ip rather than a unix socket.

Likely, your psql and postgresql have different ideas of the correct setting for unix_socket_directory. Especially seeing as you have at least two different builds of postgresql installed! You might want to make sure you're using the psql client that corresponds to your postgresql server, since they have different major versions that will have other benefits too. Failing that, you can give a unix socket directory name as the hostname, e.g. psql -h /tmp will look for /tmp/.s.PGSQL.5342.