In the wake of sequencing projects, protein function analysis is evolving fast, from the careful design of assays that address specific questions to large-scale proteomics technologies that yield proteome-wide maps of protein expression or interaction. As these new technologies depend heavily on information storage, representation and analysis, existing databases and software tools are being adapted, while new resources are emerging. This paper describes the proteomics databases and software available through the World-Wide Web, focusing on their present use and applicability. As the resource situation is highly transitory, trends and probable evolutions are discussed whenever applicable.