Help to expand the knowledge base of the family
Every family tree has been researched before, there might even be an unpublished book, and any mention of it should be hunted down diligently.
For example, research into the Risbridger family uncovered not one, but two unpublished researches about the family together with numerous documents, certificates, maps and photos
Divorce papers can be researched in Kew Records Office and can provide a mine of information about the relatives involved, and sometimes give a different story to the one passed down in the family
Google and other search engines can provide a wealth of information, but remember that not everything is on Google!