When either writing or speaking, using appropriate statistics can help prove or disprove your point. This works best with statistics from reliable resources. Each of the links provided can lead you to reliable--quotable statistics. Logically weaving statistics into your essays, papers, or speeches will strengthen your work.
For instance, the best resource for information related to population growth or racial makeup would be found under census.gov and can generally be narrowed down to specific states, counties, or cities. If you needed information about laws in a given state they may be found on state websites like scstatehouse.gov (for South Carolina).
OFFSTATS is the the most comprehensive listing of links for international statistics.