dpkg -l|grep postgresql-
ii  postgresql-client                             9.1+129                                                               front-end programs for PostgreSQL (supported version)
ii  postgresql-client-8.4                         8.4.11-1                                                              front-end programs for PostgreSQL 8.4
ii  postgresql-client-9.1                         9.1.4-0ubuntu12.04                                                    front-end programs for PostgreSQL 9.1
ii  postgresql-client-common                      129                                                                   manager for multiple PostgreSQL client versions