Blackberry Ridge Woolen Mill (just outside Mt. Horeb, WI, near Madison) will be having their semiannual open house Saturday, April 14, from 8:00 AM until 4:00 PM, tours to begin at 10 am.
Here is their info: http://www.blackberry-ridge.com/
The tours are really neat, and they have a fair amount of mill ends for sale, which I have really enjoyed spinning. They also carry some hand painted tussah silk, and some mohair and ramie top as well.