SCImago Journal & Country Rank: Journal Rankings Based on Scopus Data

The new SCImago Journal & Country Rank system utilizes data from Elsevier's Scopus database to produce a variety of scholarly journal rankings. For example, you can rank journals by their h index in a particular subject area, such as Family Practice.  The h-index is an index that quantifies both the scientific productivity and the scientific impact of a journal (it is also applicable to scientists, countries...). The index is based on the set of the journal's most quoted papers and the number of citations that they have received in others publications.

The Help page provides detailed information about the free service.