The best way to keep track of your references is to keep a record of the articles you have read. Reference management tools help you to organise your references and automatically generate reference lists or bibliographies in a variety of styles.
If you are going to keep records of large numbers of references then it will be worthwhile investing time in selecting and learning how to use a tool. There are several free web-based tools from which to choose. Some are basic tools for undergraduate study. Others are more advanced and suitable for researchers and postgraduate students.
BibSonomy is a social bookmarking service and can be used to export bibliographies in a variety of formats and feeds.
RefME is a web-based tool for generating citations, reference lists and bibliographies; there is an option for importing .ris files. It is also available as an App.
Delicious is a service designed for personal bookmarking on the web. Websites can be accessed anywhere, no matter what computer or device you are using.
More advanced tools
Colwiz is a software that helps to sort, cite and share research. You can import PDFs and references from the web to your desktop and mobile devices.
EndNote Basic is entirely web-based and allows you to store, manage and share your references, cite sources and write your papers. It is a simpler, free version of the commercial tool Endnote Desktop. (Please disregard the 'Sign in via your institutional login' option on the 'Sign In or create an account' page.)
Mendeley is a reference manager and academic social network that is fully searchable with capacity for reading and annotating PDFs on any device. It is available as web-based or as a standalone desktop version.
Proquest Flow is a cloud-based collaboration tool that allows you to collect, manage and organise your documents. You can also annotate and cite your research.
Zotero is a free bibliographic software extension for Firefox. It is also available as an extension for Chrome and Safari browsers, and as a standalone desktop version.