Here are links to Wisconsin's largest media outlets:

Newspapers:
These links take you to the paper's Letters to the Editor sites:
 
Appleton Post Crescent
Eau Claire Leader Telegram
Green Bay Press Gazette
La Crosse Tribune
Madison Capitol Times
Madison Wisconsin State Journal
Milwaukee Journal Sentinel
Oshkosh Northwestern
Waukesha Freeman

Television Stations:
These links take you to the station's viewer feedback sites:

Milwaukee:
MPTV (PBS-10 & 36)
WTMJ (NBC-4)
WDJT (CBS-58)
WISN (ABC-12)
WITI (Fox-6)
WVTV/WCGV (18 & 24)

Madison:
WISC (CBS-3)
WKOW (ABC-27)
WMSN (Fox-47)
WMTV (NBC-15)
WHA (PBS-21)

Green Bay:
WBAY (ABC-2)
WFRV (CBS-5)
WGBA (NBC-26)
WLUK (Fox-11)