I've been working towards exporting the Salesforce Schema via the Partner API to SQL Server. The current export is starting to look a lot like the Salesforce supplied ERD.
![Exported Salesforce Core Sales objects schema in SQL](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkW-IGc7GEbS7VANBlAgskcYRgbd4sMDKLMupp5ohbzd1RzQGrFX-E0b8PKjaA58A3PMnwHFiAYFQDhXSq6rh6QIIB8hl5dZ6_rWguw8UTckNUO4WoZmGAsLzludy7hdjDX0idx1ethYUB/s400/SalesforceCoreSalesObjectsInSql.png)
Note that most of the Status/Stage objects are disconnected when using the Partner API as the data has been denormalized. Also, the Partner object isn't exposed via the Partner API.