We present an extended version of a software system SIGHTS (statistical identification of groups hidden in time and space), which can be used for the discovery, analysis, and knowledge visualization of social coalitions in communication networks such as Blog-networks. The evolution of social groups reflects information flow and social dynamics in social networks. Our system discovers such groups by analyzing communication patterns. The goal of SIGHTS is to be an assistant to an analyst in identifying relevant information. The functionality of SIGHTS includes: discovery of coalitions (clusters) and their leaders; finding hidden groups using communication persistence techniques; discovering hidden groups in communication streams; matching topics of the blogs and detecting sentiments; tracking the evolution of clusters; visualization of collections of individual clusters.