Sociolinguistics:

Sociolinguistics is the study of language variation by social context. Examples of social variation in language include variation by region,

Regional dialects of American English (Part One) (http://www.ling.upenn.edu/phono_atlas/usnews/usnews1.jpg)
This is the first of a two-part link to a U.S News and World Report article on American dialects of English.

Regional dialects of American English (Part Two) (http://www.ling.upenn.edu/phono_atlas/usnews/usnews2.jpg)
This is the second part of the U.S. News and World Report article on American dialects.

by ethnicity,

American Dialect Society page of links for AAVE (http://www.americandialect.org/links.shtml)
This page offers links to other sites concerning African American Vernacular English, as well as other issues of interest to sociolinguists

Ebonics page: Center for Applied Linguistics (http://www.cal.org/ebonics/)
This site conteins several links to the writings of linguists on the issue of the use of African American Vernacular English in classrooms.

Variation in world-wide use of English (http://newsvote.bbc.co.uk/olmedia/video/events99/talkingpoint/tp01aug99.ram)
This is a BBC program about the variation of English around the world. You'll need RealAudio software to hear this one.

A Yiddish glossary (http://www.uta.fi/FAST/US1/REF/yidgloss.html#dx)
This is a glossary of Yiddish words and expressions. Since Yiddish can be called a creole language, we can see evidence of the contributions to Yiddish from German, Hebrew and other sources.

by social class,

New York Tawk ( http://www.npr.org/ramfiles/atc/19990312atc08.rmm)
Here is an excerpt from NPR with sociolinguist William Labov describing his work with New York dialect variations, and including several speech samples. Listen especially to the last one near the end of the excerpt!

by gender,

or by context of usage.

Do we need "language police" for standard English?
(http://discover.npr.org/features/feature.jhtml?wfId=1067943)
This is an except from an NPR "Talk of the Nation" program with Michael Krasny as the host, and some famous linguists as guests, including Michael Pinker and Robin Lakoff.