Mendeley's Papers has statistics about the millions of papers cited in Mendeley. This lets you use Mendeley to monitor new and popular articles in your discipline.
How does it work?
When you create your Mendeley account, you are required to choose an academic discipline. (You can change this by editing your profile.) When you upload PDFs and save citations to your Mendeley account, Mendeley anonymously connects the academic discipline with this particular paper/citation. When more people in your discipline also save the same paper/citation, it gives the connection more weight.
When browsing articles in Mendeley's Papers you can Save a Reference to your library. If there is a PDF attached that is from an Open Access journal or a publicly accessible repository, you will have the option to save the PDF to your library.