On Ancestry.com I noticed they have a new feature that finds people on other records for you automatically. They list them as 'suggested records" on the right side of the screen.
When you search for someone and then click on the record you found, they run a program in the background they call Ancestry Metrics. It looks for that same person, based on the name and date of birth and then automatically gives you a list of the other records.
This is a really wonderful addition to their service as you can literally find sometimes a half dozen records that are probably the person you are researching.