Here are a few databases to get you started:
Academic Search Complete - Academic Search Premier (ASP) contains indexing and abstracts for more than 8,200 journals, with full text for more than 4,500 of those titles. Academic Search Premier contains unmatched full text coverage in biology, chemistry, engineering, physics, psychology, religion & theology, education, English literature, etc
Communication and Mass Media Complete - Communication & Mass Media Complete offers indexing and abstracts for nearly 600 titles, nearly 300 of which are also available in full text. Also provides a Communication Thesaurus, comprehensive reference browsing (i.e. searchable cited references for peer-reviewed journals covered as "core"), and over 3,000 Author Profiles with biographical data and bibliographic information.
Google Scholar - Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, patents, 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.
JSTOR - Provides image and full-text online access of core academic journals in a variety of disciplines in the sciences, social sciences, and humanities. The following collections are accessible: Arts and Sciences Collections I-X; Life Sciences Collection; and Public Health Reports.
ProQuest Research Library - Research Library is a comprehensive database available through the ProQuest online system. It indexes and abstracts general interest magazines and scholarly journals, trade publications, magazines and newspapers in the social sciences, humanities and sciences. The database includes more than 3820 titles -- over 2550 in full text -- from 1971 forward. Topics covered include arts, business, children, education, general interest, health, humanities, international studies, law, military, multicultural studies, psychology, sciences, social sciences, and women's interests.
ProQuest Dissertations and Theses - PQDT provides online access to over 2 million dissertations and master's theses, many of which are available in full text for immediate downloading. Citations are available for dissertations dating from 1861 and full text online from 1997 for over 1,000 schools submitting to the ProQuest UMI database. More than 55,000 new citations are added to the database every year.