Knowledge sharing across community boundaries has been discussed in literature as an important source of new knowledge and innovation. Different studies point out the difficulties and specific requirements to be considered in cross-community contexts. In contrast, the development and empirical evaluation of concrete methods and systems incorporating these insights has been little addressed. This paper discusses the main challenges of supporting cross-community knowledge exchange and presents an approach to addressing them based on collaborative knowledge visualization. The developed method enables the visualization of implicit structures of personal and community knowledge and their use for multi-perspective access to community information spaces. The results of an empirical evaluation in a comparative laboratory study suggest that this method provides valuable support for facilitating crosscommunity knowledge exchange.