The following documents contain development and configuration details for the Postgres 7.x Database, the documents intent is to provide a side by side comparison to Oracle 8i configuration and Development, however they are also written in such a way to be readable as a stand-alone document, thus knowing Oracle 8i is not a prerequisite
While Oracle may have the widest market penetration and superior technical product, its legal production cost is very much limited to high-end systems, although there are "individual" (almost free) liceneses available for Oracle, in order to comply with the legal production requirements, the license costs are high.
Besides initial license costs, maintaining an Oracle database is no simple task, its functionality and performance comes at another price which on various fronts proves to be unnecessary, in other words true overkill; here is where a simple SQL-compliant Database implementation like Postgres proves to be more than enough without all the "bells and whistles" Oracle provides.
Other widely used systems like Sybase or SQLServer still present a relative high-cost, so if you are going to pay for a product you might as well bite the bullet and go for the more widely supported database; supported in the sense of : available qualified personnel, alternative feature availability (Oracle Applications),etc.
In the realm Open-Source database systems where licensing costs are null, Postgres presents a clear advantage over other systems like mysql and interbase.