Internships.com has over 13,000 listings. You can search by keywords with terms related to industry, major, etc., as well as by location or company name
Internships USA is the largest internship site on the web with more than 3,000 organizations offering internships for college and law students. Select "The Internship Series Online" username: work password: learn
Go here for a comprehensive webpage on researching, finding and being successful in an international internship. For more general information about going abroad.
Go here to view a listing of internships by Field and Region.
Summer Internship and Fellowship Opportunities for Students of Color -- A comprehensive 76-page PDF document with text, links, and contact info.
Internships, Fellowships and Scholarships in Education