The Open Geospatial Consortium (OGC) exists to define interface standards such as the Web Mapping Service (WMS) standard, or Web Feature Service (WFS) standard. These are standards that define how programmers should create software to provide such a service.
So for example, OGC defines the WMS standard, programmers write a piece of software called MapServer that can create a WMS service according to this standard, lastly I as a user take this MapServer software, install it on a server add my data and create a service.
Similarly other programmers can write a client (for example QGIS or ArcMap) that understand the OGC WMS standard, such that my MapServer WMS service can be viewed and queried.
INSPIRE (as noted by Mapperz) is legislation, that requires Government and Public bodies within the European Union, to make important spatial dataset information available. It is not a standard or a service. INSPIRE makes available a number of technical guidance documentation intended to assist such government bodies make their information available using for example OGC services like CSW for Discovery (metadata), WMS for Viewing (images of data), WCS or WFS for Download (get the raw data). The EU itself only gathers and republishes INSPIRE metadata through a portal. INSPIRE services are provided by the government bodies themselves.
Global Earth Observation System of Systems (GEOSS) is conceptually similar to INSPIRE, except it is not legislation, with the intention of providing a means of discovering (metadata) and accessing (viewing) Earth Observation data. It has a wider spatial scope, e.g. it is global as opposed European Union (INSPIRE), but covers fewer types of data.