The Horus project seeks to develop a communication system addressing the requirements of a wide variety of distributed applications. Horus implements the group communications model providing (among others) unreliable or reliable FIFO, causal, or total group multicasts. It is extensively layered and highly reconfigurable allowing applications to only pay for services they use. This architecture enables groups with different communication needs to coexist in a single system. The approach permits experimentation with new communication properties and incremental extension of the system, and enables us to support a variety of application-oriented interfaces. Our initial experiments show good performance.