SSRS is a wonderful tool for quickly retrieving data from many different data sources and presenting the data to the user at a run-time decided format. One area where SSRS often falls short is when the underlying data needs to come from several different sources. Perhaps we want to retrieve data from the General Ledger which is in Oracle, and join that against a list of departments and employees which are stored in SQL Server for us to display in one table. When this happens, we are unable to join them into one dataset without the use of a linked server.
I've put together a sample SSRS DPE project and uploaded it to Code Plex as a starting point for any interested developers to work from. Depending on the specific needs of the project I'm certain additional development will be required, but my goal is to create a useful starting point for anybody that needs to use SSRS to report data coming from two or more different databases.