OnlineUniversities.com offered a useful list of Search Engines.   The site says that:

‘ Undergraduates and grad students alike will appreciate the usefulness of these search engines that allow them to find books, journal articles and even primary source material for whatever kind of research they’re working on and that return only serious, academic results so time isn’t wasted on unprofessional resources.’

Categories include:

  • General
  • Meta Search
  • Databases and Archives
  • Books and Journals
  • Science
  • Math and Technology
  • Social Science
  • History
  • Business and Economics
  • Other Niches
  • Reference

Check it out!  http://www.onlineuniversities.com