You will want to collect, store, organise and annotate references either in a web account or on a desktop.
Consider whether the software offers you the ability to liink to full text, documents and websites and documents as well as cite your references and create bibliographies.
Many allow sharing your references, PDF highlighting, collaboration and social networking.
You should also be able to import references, for example for a list of search results in a database as well as manually create references.