pgAdmin III is the most popular and feature rich Open Source
administration and development platform for PostgreSQL, the most
advanced Open Source database in the world. The application may be used
on Linux, FreeBSD Solaris, Mac OSX and Windows platforms to manage
PostgreSQL 7.3 and above running on any platform, as well as commercial
versions of PostgreSQL such as Mammoth PostgreSQL, EnterpriseDB Postgres
Plus Advanced Server, Greenplum Database and Bizgres.

pgAdmin III is designed to answer the needs of all users, from writing
simple SQL queries to developing complex databases. The graphical
interface supports all PostgreSQL features and makes administration
easy. The application also includes a syntax highlighting SQL editor, a
server-side code editor, an SQL/batch/shell job scheduling agent,
support for the Slony-I replication engine and much more. Server
connection may be made using TCP/IP or Unix Domain Sockets (on *nix
platforms), and may be SSL encrypted for security. No additional drivers
are required to communicate with the database server.

pgAdmin III requires wxPython and PostgreSQL.