In recent years, various kinds of distributed resource sharing setups have been proposed by taking social relationships into consideration. These dissimilar resource sharing setups are tagged as Social Cloud. These setups have appeared in various distributed computing forms such as community cloud, grid, volunteer computing and network services. Such setups are discrete in nature, and hence, do not conceptualize the totality of the Social Cloud concept. In fact, it is difficult to conceptualize Social Cloud without a general framework. There are three main objectives of this work. First, to present a general framework of Social Cloud. Second, to report various Social Cloud setups with corresponding architectural prototypes and current trends. Third, to discuss research challenges.