Scopus (http://www.scopus.com/) has recently released TopCited
(http://info.scopus.com/topcited/), a free service informing about the
most-cited recent articles (2004-2008)in various disciplines. Users can also view the top 20 articles from the past 3, 4, or 5 years in one
of the 26 subject areas, and view the authors' institutions on a Google Map.