Flickr is a photo sharing website. It can display geotagged photos on map. Flickr uses OSM maps for some parts of the world, eg Beijing and Baghdad.
Photos on Flickr can be given machine tags to link to a specific object in OSM. Flickr will read some of the tags of that object to describe the photo.
eg to link to an OSM way / node:
More details: 
This web application is made by 3liz to help contributors to link pictures from their Flickr Account to OpenStreetMap objects. You can log in with your Flickr account, and then you will be able to use a map to search for OSM objects and create machine tags easily. http://demo.3liz.com/osmflickr/
Source code is on github: https://github.com/3liz/osmflickr
Web application built by User:Pgiraud.
Helps user to link easily Flickr photos to elements on the map. Built with d3js on top of iD editor for interaction.
Source code is on github : https://github.com/pgiraud/flickr4osm