A listing of gazetteers available at the Family History Library can be found online. These gazetteers can help you to locate the parish where your ancestors attended church. Once you have determined the parish, you can check the Family History Library Catalog for holdings of that locality. The Family History Library has many records of Württemberg in its collection.
Here is a website which divides modern Baden-Württemberg into regions (Regionen), districts (Regierungsbezirke), counties (Landkreise), cities and villages (Städte and Gemeinden) and into administrative entities (Verwaltungsregionen)
see also http://de.wikipedia.org/wiki/Verwaltungsgliederung_W%C3%BCrttembergs for older jurisdictions