I do a presentation (and a class) called "SQL Server for the Oracle DBA". It's a non-marketing overview that gives you the basics of working with SQL Server if you're already familiar wtih how Oracle works. This class and these links DO NOT help you with "Why should I use Oracle/SQL Server instead of Oracle/SQL Server" - I'll assume you're already there, and if not, there are LOTS of sites to help you make that decision.
Although these links might contain slight marketing slants (I don't control them) I've tried to get the best links I can. Feel free to comment here to add more/better links.
As such, these aren't links that help you work with Oracle - they are links to help you work with SQL Server. Some of them contain more information than you actually need, others don't have near enough. Taken together (and with the class) you're able to get done what you need to do.
"Practical SQL Server for Oracle Professionals" - A Microsoft Whitepaper, probably the best place to get started: http://download.microsoft.com/download/6/9/d/69d1fea7-5b42-437a-b3ba-a4ad13e34ef6/SQLServer2008forOracle.docx
Free Training: http://technet.microsoft.com/en-us/sqlserver/dd548020.aspx
Classroom training (will cost you): http://www.microsoft.com/learning/en/us/course.aspx?ID=50068A&locale=en-us
Terminology Differences: http://www.associatedcontent.com/article/2383466/oracle_and_sql_server_basic_terminology.html
Datatype mapping between Oracle and SQL Server: http://msdn.microsoft.com/en-us/library/ms151817.aspx
The "other" direction - can still be useful for the Oracle professional to see the other side: http://blog.benday.com/archive/2008/10/23/23195.aspx