There are few possibilities:
Master/Master replication (Bucardo), Master/Slave replication (Slony)
Using foreign data wrappers - you can access a any table from other databases. 9.2 provide comfort FDW read only driver, 9.3 contains read/write FDW driver
CREATE EXTENSION postgres_fdw ; CREATE SERVER omega FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host 'localhost', dbname 'other_database'); CREATE USER MAPPING FOR pavel SERVER omega; CREATE FOREIGN TABLE oo (a int) SERVER omega; postgres=# EXPLAIN ANALYZE VERBOSE SELECT * FROM oo WHERE a BETWEEN 1 AND 100;
FDW is probably most simple solution how to share data.