I recently came across a presentation given on migrating a very large database (as in, tables with 1.8 billion rows) from Oracle to PostgreSQL. It describes some of the issues they had along the way, including having to move from Linux to OpenSolaris due to stability issues.
One of the more interesting challenges they had to solve was the lack of support for partitioning in PostgreSQL. Oracle allows you to partition tables, so for example if you had a large table, you can cluster the data into various segments - dates in their case.
A collection of tools that support PostgreSQL, courtesy of a commenter in this Slashdot post (both commercial and non represented here).
pgAdminIII Side note on this one - there’s a beta of the new version out, the UI is quite improved.
EMS Postgresql Manager
Sybase Power Designer
ERWIN data modeller
CASE Studio 2