Caching on the edge of the Internet is becoming a popular technique to improve the scalability and efficiency of delivering dynamic web content. In this paper we study the challenges in designing a large scale cooperative edge cache network, focusing on mechanisms and methodologies for efficient cooperation among caches to improve the overall performance of the edge cache network. This paper makes three original contributions. First, we introduce the concept of cache clouds, which forms the fundamental framework for cooperation among caches in the edge network. Second, we present dynamic hashing-based protocols for document lookups and updates within each cache cloud, which are not only efficient, but also effective in dynamically balancing lookup and update loads among the caches in the cloud. Third, we outline a utility-based mechanism for placing dynamic documents within a cache cloud. Our experiments indicate that these techniques can significantly improve the performance of the edge cache networks.