If we break Indiana into rough geo-political regions:
Gary-Hammond
A blue collar (more steel is made in Lake County than any other part of the U.S), heavily unionised area and by far the most Democratic part of Indiana
South Bend-Elkhart
The South Bend area is very "ethnic" (the largest Hungarian Community in the U.S is in the area) and fairly Blue Collar, while Elkhart is solidly Republican. Overall the region swings about *a lot*
Fort Wayne
With the exception of a few blue collar districts in Fort Wayne itself, Fort Wayne (along with it's suburbs) is a GOP stronghold (and has been since the Civil War)
The Corn Belt
Sterotypical Indiana: lots of farms and small towns, "rednecks", religious zealots... The Cornbelt covers most of the state and is the backbone of the Indiana GOP (and has been Republican since the Civil War).
Indianapolis and Suburbs
While Indianapolis itself leans Democrat, the wealthy suburbs of Indianapolis are the most Republican parts of the state with several counties voting for Bush with over 70% of the vote.
Muncie
The "Middletown" area is fairly centrist and tends to swing around a bit... (Clinton in '96, Bush in '00) it also has a quirky independent streak (Perot did well in the Muncie area in '92)
Indiana Coalfield
Basically an extension of the Southern Illinois Coalfield, the area includes Vermillion County (after Lake, the most reliably Democratic county in Indiana) and overall leans Democrat. The largest City (Terre Haute) is a traditional hotbed of Populism.
Ohio Valley
A traditional swing area, the Ohio Valley tends to be socially conservative and economically leftist and has a habit of producing large swings without little warning.
Democrats often do well in the (very) blue collar counties in the Southeast of the area.
Parts of this analysis are no longer true. Lake County is no longer the most Democratic area in Indiana; that status is now owned by Marion County. The Gary area has trended substantively to the right in recent years. Democrats have completely collapsed in the Coalfield and Ohio Valley, both of which are now Safe R, and the "Middletown" area is now Safe R as well. Indianapolis is now a Safe D city, and the suburbs of Indianapolis (Hamilton County) are no longer the most Republican region of the state; the Cornbelt holds that status. Hamilton County could even flip Democratic in the next decade if current trends continue.
