Internet pervasive services call for flexible supportsto enable a wide degree of collaboration. On the onehand, many people are connected to the Internet andsurf the Web not only to retrieve information, but also tocarry out several kinds of different tasks via the on-lineservices. On the other hand, the Internet is likely to besoon populated by software agents that will act in behalfof users, “intelligent” enough to achieve the better resultwithout boring their users. In this paper we present aWeb-based modular architecture that permitsinteraction and collaboration among people and agents,leading to a more fruitful exploitation of the capabilitiesoffered by the Internet. A negotiation application basedon auctions is used to show the advantages of theproposed architecture.