Atom Syndication Format is an XML language used for web feeds very similar to RSS.
http://en.wikipedia.org/wiki/Atom_%28standard%29
Syndication Techniques
Get access to data on 8,109,460 websites that are Atom Customers. We know of 3,099,498 live websites using Atom and an additional 5,009,962 sites that used Atom historically and 1,607,486 websites in the United States.
Get a list of 8,109,460 websites using Atom which includes location information, hosting data, contact details, 3,099,498 currently live websites and an additional 1,726,198 domains that redirect to sites in this list. 5,009,962 sites that used this technology previously and 1,607,486 websites in the United States currently using Atom.