Peer-to-peer file sharing has become popular for many kinds of resource location and distribution applications including file sharing, distributed computation, multi-media messaging and content distribution. Peer-to-peer approaches also have significant potential for supporting large scale, decentralised service oriented computing. This chapter discusses each class of contemporary P2P architecture in turn and discusses the suitability of each architecture class for supporting service oriented computing. Future trends in peer-to-peer architectures are then discussed and multi-layer peer-to-peer architectures are highlighted as a promising platform for supporting service oriented computing. This chapter then concludes with a discussion of outstanding issues that must be addressed before peer-to-peer architectures can offer adequate support for service oriented computing.