A distributed architecture consists of multiple components separated by process, machine, or network boundaries.
The three main types of distributed architectures are pipeline, client-server, and peer-to-peer.
The Peer-to-Peer Architecture consists of multiple component called peers. A peer is both a client and a server. For more information, see http://en.wikipedia.org/wiki/Peer2peer.
There are many design patterns that show up in distributed systems. Here are a few:
There are also several important architectures, including:
Open Distributed Processing
CORBA
COM/DCOM
Service-Oriented Architecture