The Public Library in Science (PLoS) articles now include a metrics tab– “Article-Level Metrics“–that allows for evaluation of research impact. Available data includes:

• Article usage statistics – HTML pageviews, PDF downloads and XML downloads
• Citations from the scholarly literature – currently from PubMed Central, Scopus and CrossRef
• Social bookmarks – currently from CiteULike and Connotea
• Comments – left by readers of each article
• Notes – left by readers of each article
• Blog posts – aggregated from Postgenomic, Nature Blogs, and Bloglines
• Ratings – left by readers of each article