Yes you can use any number of data providers in the same report.
you just need to add new data provider and link the objects,from different data providers.
this all you can perform in the Data Manager itself.I am giving the steps as follows:
1.Right Click and Choose "New Data Provider" in the Data Manger.
2.Create new Data provider.
3.Link the common objects from the Data Providers.

Linking can be done at "View Data" dialog box,in definition Tab.

hope this will help,else contact me if u hav any doubt