I have found a really useful white paper, Eileen  and I receive a technical roll up mail sent to us on a regular basis part of Augusts was a new white paper that provides a comparison of SQL Server 2005 and Oracle.  It gives the main features and points of each and highlights the differences it also compares key features.  If you are an Oracle professional this is a really useful white paper.  I think any SQL professionals wanting to know about some of Oracle’s features may also find it useful. I would like to give you an overview of some of the areas covered by the white paper.
The Abstract says it is targeted at the Oracle professional who want to use their Oracle knowledge to manage SQL Server or to aid in the preparation to migrate from Oracle to SQL Server.  It gives a comparison of database architectures; other areas include backup, database security, management options and high availability.  The detail it goes into is reasonable with diagrams where appropriate.  This would have been useful last year when I did some work with a financial company in London who had Oracle back end with SQL Server Analysis Services on the front.  They did not have any in depth SQL knowledge so this would have been useful to them. 
Also don’t forget the books online are available for down load they have just been updated in July you don’t even need to install the product.  If you want to use SQL server without installing it then the online labs are available.