Find out who travelled along with you. Enter your flickr photos url and then select a set from the drop down list. We'll then find out who else took photos near you at about the same time. You can only use this app currently if you have sets defined, and have photos within those sets that are geocoded. I'll change it later to accept a date range.
If you don't know where to start, try my url: http://flickr.com/photos/bluesmoon/, and my London '06 set.