Getting startedProbably my favorite resource on style is Eckert (2008)--here's a summary. That's the Eckert paper on indexical fields (find more of Penny's stuff on her website). You can see my exploration of the indexical field of speech tempo by looking at this web-based indexical field. (And/or reading my paper on the social meaning of tempo. Or a short, early hand-out on tempo.)
You can find my NWAV 2010 paper here: Variation in speech tempo: Capt. Kirk, Mr. Spock, and all of us in between.
You may also want to check out these class notes for a seminar on style itself (though a lot of them are on specific projects). Or these notes from an earlier class on variation, which gives good background on issues of style.
One of the best places to look when you're investigating variation and style is YouTube. Here's my how-to for getting YouTube into Praat. Because of compression, you won't be able to see some finer issues, but there's still plenty to look at exploratorily.
Other excellent readings include Zhang (2005) on Beijing Yuppies and lots of Podesva.