Industry uses

During the late 1990s and early 2000s, several industries started to use the term "extranet" to describe central repositories of shared data made accessible via the web only to authorized members of particular work groups.

For example, in the construction industry, project teams could login to and access a 'project extranet' to share drawings and documents, make comments, issue requests for information, etc. In 2003 in the United Kingdom, several of the leading vendors formed the Network of Construction Collaboration Technology Providers, or NCCTP, to promote the technologies and to establish data exchange standards between the different systems. The same type of construction-focused technologies have also been developed in the United States, Australia, Scandinavia, Germany and Belgium, among others. Some applications are offered on a Software as a Service (SaaS) basis by vendors functioning as Application service providers (ASPs).

Specially secured extranets are used to provide virtual data room services to companies in several sectors (including law and accountancy).

There are a variety of commercial extranet applications, some of which are for pure file management, and others which include broader collaboration and project management tools. Also exist a variety of Open Source extranet applications and modules, which can be integrated into other online collaborative applications such as Content Management Systems.

http://en.wikipedia.org/wiki/Extranet