I hear lots of amateurs describing interference and other problems on
HF, but no one seems to be triangulating the offending stations. I am
guessing that the real secret was in their communications with the
'spotters' to triangulate the positions.

Adcock arrays http://www.airwaysmuseum.com/HF%20CR%20DF%201.htm
http://members.aol.com/BmgEngInc/Adcock.html
worked quite well, but they require precision in construction, as well as
the site.
For VHF/UHF, there are all sorts of things available
N0MKJ and I used to hunt with the "fox-copter", featured in the 3/94 73
magazine.

Here's some references in 73 magazine:
http://www.pejla.se/ardf_litteratur.htm

And a bunch of links to play with:
http://www.dxzone.com/catalog/Operat...ction_Finding/