Biographies Online - Good source of scientists and others.
Eric Weisstein's World of Scientific Biography - A database of very brief biographies for over 1,000 figures in science.
PLOS: Public Library of Science - A collection of open access scientific journals on biology, genetics, pathology, botany, etc.
Nobel Prize Internet Archive - Biographies of Nobel Prize winners, with links to other sites containing information.
Biographies - Infoplease website. Organized by category (e.g. Arts and Entertainment, Science and Technology, etc.). Info
Biography.com - Arts & Entertainment's Biography Web site. Useful for current or popular personalities. You may be able to find video clips about the individual you are researching here