Google Scholar provides a site where you can search across many sources including peer-reviewed papers, theses, abstracts, books, and articles, from universities, academic publishers, professional societies and other scholarly organizations.
At ERIC teachers can search a database of over one million citations on education topics going back to 1966. Over 100000 full text articles are available for free.
Provides links to over 200 free, full text quality controlled scholarly journals on Teaching and Education. Many of the journals are searchable on the DOAEJ site, although for some you have to go to the individual journal site to search for articles.