"the creation and study of new metrics based on the Social Web for analyzing, and informing scholarship."
-from "The Altmetrics Manifesto"
Looks at data from...
Twitter Facebook Mendeley Zotero
News outlets Blogs Delicious Scopus GitHub
Wikipedia YouTube PubMed CrossRef SlideShare
"You can sign up for a Google Scholar Citations profile. It's quick and free.
Free, open source tool. Sign up for an account, import work from various sources, and see your profile. Include all your scholarship (articles, blog posts, datasets, code, websites) and find out who is interacting with your work and how.
For-profit startup that offers their API to publishers, repositories, and scholars; some uses are free, others (like their Explorer product) cost money. I'd like to highlight their free Bookmarklet, which allows you to view altmetrics for any article. Note: it only works on PubMed, arXiv or pages containing a DOI.