Module Release Announcement: Page Not Found Reports 7.x-1.0
The Page Not Found Reports module adds a couple of admin reports about 404 errors. The Drupal core comes with a report of the top 404s, but this only gives the path and number of requests. The reports added by this module include information about referring pages, and the number and frequency of 404 errors. The referrer information is especially helpful in finding what other sites may be linking to images that were missed during a site migration.
The Drupal 7 port is thanks to justanothermark. There is one feature that still needs to be ported: benclark added an Operations column to the reports to make it easy to add redirects for paths that result in a 404, but this is only in D6 right now.