Academic Search Premier is housed within the EBSCO system. This means that it has a very user-friendly search interface. Academic Search Premier covers a wide range of disciplines. It does not cover as many publications as a specialized subject database would, but it is still an excellent place to start your research.
EBSCO is an umbrella for 80+ databases on every imaginable subject, from business to education to nursing to sociology to literature. When you click on the link, browse the list of databases and choose ones you would like to search.
If you want to be daring, "Google-ize" EBSCO by selecting all databases to search at once. Do this when you are uncertain of which database to choose. This search will show you the degree to which databases cover your topic.
Proquest is an umbrella to 17 databases, plus e-books and newspapers. It covers the humanities, the social sciences, the sciences, and business. Both general interest and scholarly publications are included.