finding out about databases and tables

Hi,

I am relatively new to Postgresql.  I have Postgresql running on a Linux server, and I need to find out the names of
alldatabases, and all tables within those databases, so I can start querying for data, and spool those results to a
filefor export.  Can someone please tell me what commands I should run as a root user to find out this information, and
querythe databases for spooling to a file? 

Thanks,

Ken