ACRL has released Keeping Up With… Altmetrics.
Here's an excerpt:
Into this setting, enter altmetrics. Altmetrics is an emerging category of impact measurement premised upon the value of "alternative metrics," or metrics based distinctly on the opportunities offered by the 21st century digital environment. Originally defined in contrast to the more established field of bibliometrics, altmetrics is fast becoming a fluid area of research and practice, in which various alternative and traditional measures of personal and scholarly impact can be explored and compared simultaneously.
In this Keeping Up With… edition, we look at key points in the rapid development of altmetrics, from its 2010 origins to its more recent relevance to librarians and administrators.
If you are interested in altmetrics, also check out the Altmetrics Bibliography.