This impact factor "is a measure reflecting the average number of citations to articles published in science and social science journals." You can search by journal on this site.

This portal "includes the journals and country scientific indicators developed from the information contained in the Scopus® database (Elsevier B.V.). These indicators can be used to assess and analyze scientific domains."

Provides impact factor lists for 2008 through 2014, plus an article on how to get a journal indexed. Scroll down at the main link (http://www.citefactor.org/page/impact-factor) to read the criteria for determining the impact factor. Click on "articles" in the left navigation bar to identify articles' number of "views" (called "real time impact factor").

OMICS International publishes over 700 open access journals a year in the fields of Medicine, Engineering, the Sciences, Business and Management, and Social and Political Sciences. For many journals, they provide a "citations report" and offer an impact factor score. I have contacted OMICS for a description of the criteria they use to determine those reports (Aug. 10, 2015)

Still in "demo" phase, "MESUR studies Science (with capital S) as a social system from large-scale usage data collected from some of the world’s most significant publishers, aggregators and institutional consortia." With grants from Mellon Foundation and NSF, MESUR now has a database with over 1B "article-level" usage events." They also have COUNTER usage reports. Part of their criteria extend beyond the scholarly environment to practical applications.

An academic research project co-founded in January 2007 by Carl Bergstrom and Jevin West, and sponsored by the West Lab at the Information School and the Bergstrom Lab in the Department of Biology at the University of Washington.

Paul Wouters, in 2013, argued that journal impact factors should be assessed in conjunction with a number of additional considerations. Provides bibliography to earlier articles on this subject.

The Journal Usage Factor (UFJ) project is a joint initiative between the United Kingdom Serials Group and COUNTER. The goal, as with MESUR, is to focus on usage rather than citations, moving beyond the scholarly environment to practical applications. One section of the article compares usage to citations.