CHILDES Dialects  Samples of speakers of many dialects and first languages, all reading the same English text, 69 words long.

http://polyglot.lss.   DARE excerpts: Arthur the Young Rat and spontaneous speech

http:/ / -- small # of longer spontaneous speech samples from DARE

http://www.ic.arizona .edu/%7Elsp/index.html  Some varieties have samples; not all   New Zealand, Australia, "England", "American"; all reading the same passage, 3-4 sentences long.  "American", various UK, other languages Language%20Variation.html:  videos of Ocracoke, Lumbee; discussion of Spanglish and verb tenses


http://accent.gmu. edu/browse_maps/namerica.php

Other links are possible from Karen Chung's homepage, under 'accents'

Also, try the links from the American Dialect Society

Also, have a look at the MLA's wonderful, interactive color maps of languages in America.   You can type in zip codes and get user-friendly but detailed language breakdowns based on census data of the 30 most commonly spoken languages in the US.