The rapid growth of scholarly information resources available in electronic form and their organisation by digital libraries is proving fertile ground for the development of sophisticated new services, of which citation linking will be one indispensable example. Many new projects, partnerships and commercial agreements have been announced to build citation linking applications. This paper describes the Open Citation (OpCit) project, which will focus on linking papers held in freely accessible eprint archives such as the Los Alamos physics archives and the other distributed archives, and which will build on the work of the Open Archives initiative to make the data held in such archives available to compliant services. The paper emphasises the work of the project in the context of emerging digital library information environments, explores how a range of new linking tools might be combined and identifies ways in which different linking applications might converge. Some early results of ...