From the Google Scholar Web site:
What is Google Scholar?
Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Use Google Scholar to find articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles available across the web.
The pilot project is now being vastly expanded. Interested? On your own behalf or on behalf of students you deal with who are heading to university? Then get an update and thoughtful opinion via this article on Gary Price's ResourceShelf: Google Scholar is Now Open to All Libraries.
And there's more, a great deal more, in Barbara Quint's story on Information Today, Inc.'s NewsBreaks: Library Collections Linked on Google Scholar for Free.