If you are interested in phonological and lexical variation in English, check out the dialect survey of North American English dialects (conducted by Bert Vaux).

From the web site:

The dialect survey is an expansion of an initiative begun by Professor Bert Vaux at Harvard University. Dr. Vaux prepared an earlier version of this survey for his Dialects of English class at Harvard in 1999. The survey has since been revised and expanded for a larger, lay audience.

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The Dialect Survey uses a series of questions, including rhyming word pairs and vocabulary words, to explore words and sounds in the English language.

Bert Vaux has also started a new English dialect survey which can be taken at: http://www3.uwm.edu/Dept/FLL/linguistics/survey/ (login required).