Yes, Mildred Fish Harnack was a fairly well-known member of the "Red Orchestra," a resistance group. A book about her was written over a decade ago:
Shareen Blair Brysac. Resisting Hitler: Mildred Harnack and the Red Orchestra. New York: Oxford University Press, 2000.
Wisconsin Public Television did a documentary on her, which can be viewed online:http://wpt2.org/naziresistance/http://video.wpt2.org/video/2243188017/
The UW Archives has an online exhibition on her:http://archives.library.wisc.edu/uw-archives/mfh/sectionpage...
A relative has posted some material here:http://users.wfu.edu/ecarlson/mildred/
Wikipedia has a short treatment of her life and work:http://en.wikipedia.org/wiki/Mildred_Harnack