At the end of the 19th century, Encyclopaedia Britannica was in financial trouble. But thanks to a cooperation with the London Times it was possible to reach a lot of new buyers by massive advertising. This worked well, but the reprinted content became increasingly dated. A journalist joked: ‘The Times is behind the Encyclopaedia, and the Encyclopaedia is behind the times.’ 
Among the many cooperations in the history of EB there was also the School Advancement Program in the 1950s. A school got a free set of Britannica Junior if fifteen sets were sold via the school. The EB company obtained names and addresses of parents from the school, and the company claimed that the school was subsidizing the purchase of a set. The Federal Trade Commission reacted with a Cease and Desist Order. 
Wikimedia Foundation in a few cases had a cooperation with a commercial enterprise in order to make some money, beyond the donations it essentially lives from. In 2009 it was made public that the Foundation signed an agreement with Orange. The telecom company paid for the Foundation’s support to improve incorporation of Wikimedia content into Orange products.  But in the end there were never much of these cooperations because the Foundation does not really have to offer something: the content itself is free, anyway.
Wikimedians use most commonly the expression ‘partnership’ to denote a cooperation with an institution that provides pictures. A notable early example is the 10,000 paintings (public domain) given by the German enterprise Directmedia in 2005. The American mineral dealer Robert Lavinsky helped with more than 50,000 pictures of minerals from his website. The biggest donation from a single institution are the 80,000 photographs by the German Federal Archives (Bundesarchiv), at the end of 2008.
In a different kind of cooperation, institutions like museums allow Wikimedians to visit them and take pictures by themselves. The initiative Wiki loves arts in the Netherlands collected in this way more than 4000 pictures (June 2009).
Some institutions try to gain a special benefit from the partnership. Bundesarchiv, for example, uploaded versions of its photographs in low resolution. The idea is that a high resolution version (maybe for a poster) can be bought from Bundesarchiv. Unfortunately, according to Mathias Schindler from Wikimedia Deutschland, Bundesarchiv has no intention to free more pictures. It was somewhat unhappy about people who reused the pictures without full respect to the licence obligations.
There are still a lot of opportunities for Wikipedia and other Wikimedia projects. It is to hope that the Wikimedia Bookshelf Project in future will provide more material for people who would like to cooperate.
 Harvey Einbinder: The Myth of the Britannica. MacGibbon & Kee, London 1964 (reprint 1972), pp. 43-45.
 Harvey Einbinder: The Myth of the Britannica. MacGibbon & Kee, London 1964 (reprint 1972), p. 323.