The WildList Organization collects monthly virus reports from anti-virus experts around the world. The data from the reports are compiled to produce The WildList - a list of those viruses currently spreading throughout a diverse user population. A virus that is reported by two or more of the WildList reporters will appear in the top-half of the list and is deemed to be 'In the Wild'.
In recent times, the list has been used by Virus Bulletin and other anti-virus product testers as the definitive guide to the viruses found in the real world.
An anti-virus product is expected to score 100% detection against this group of viruses. The WildList website can be found at http://www.wildlist.org.
The latest available WildList can be found here.