Here is list of some of the larger bourbon distilleries in Kentucky. Some offer tours, etc. Click links for their websites:
Woodford Reserve

Bulleit Bourbon, Lawrenceburg, Kentucky
Buffalo Trace, Frankfort, Kentucky. Described by many as one of the most beautiful distilleries.
Four Roses, Lawrenceburg,Kentucky. Nestled into a little corner not far from the Bluegrass Parkway.
Eagle Rare Franklin County, Kentucky
Heaven Hill Mega producer    
Jim Beam another mega producer
Makers Mark, Loretto, Kentucky
Old Rip Van Winkle: Part of Buffalo Trace, this is the source of Pappy Van Winkle Family Reserve, the rarest, finest bourbon in the world. This is, of course, my opinion, but if you don't agree, you know nothing about bourbon ;)  
Town Branch, Lexington, Kentucky: One of the newest distilleries, Town Branch is located at the edge of Downtown Lexington (appropriately at the edge of the Distillery District)
Wild Turkey, Lawrenceburg, KY
Woodford Reserve (previously called Labrot and Graham), Versailles, Kentucky. A truly beautiful distillery, top to bottom. Don't miss this one if you're visiting.

A few craft distillers:
Barrel House, Lexington, KY Craft distiller in Lexington's Distillery District
Limestone Branch, Lebanon, KY 
Old Pogue, Maysville, KY This one is a bit further out--about an hour and a half northeast of Lexington on the Ohio River. Maysville, historically, played major role in the bourbon trade.
Willett, Bardstown, KY