Attempts to evaluate the influence of scholarly periodical and mapping the structure of academic research.
Journal Citation Reports (JCR)
JCR presents quantifiable statistical data that provides a systematic, objective way to evaluate the world's leading journals and their impact and influence in the global research community. It is the recognized authority for evaluating journals. See also: http://thomsonreuters.com/products_services/science/free/essays/impact_factor/
Science Watch (Thomson)
Provides a look at highly cited research straight from the source.
Journal-Ranking.com
Red Jasper's Center for Journal Ranking (CJR) provides ranking for more than 7,000 journals from all disciplines.
SCImago Journal and Country Rank (SJR)
A portal that includes journals and country scientific indicators developed from information contained in the Scopus database.