The Collaboration Search has two different searches that allow you to find collaborations between individuals and titles.
The "Two People in the Same Title" search will return results for titles two individuals were both credited with. To find out which titles Tom Hanks and Meg Ryan were credited for, enter the names in the fields "Name 1" and "Name 2" and click "Search". This search will return all the titles both individuals were both credited for.
The "Two Titles with the Same People" search will return results for two titles and any individuals who were credited for both of these titles. To find out who worked on both Batman Begins and The Dark Knight, enter the two titles in the fields "Title 1" and "Title 2" and click "Search". This search will return all the IMDb pages for individuals who were credited for both titles.