I recently found a nice little summary of referrer-related settings in Firefox, which were modified heavily in Firefox 28. (NB: little history reminder, the settings names spell referer with just one r, as it was originally misspelled)
0 = always send,
1 = send if base domains match,
2 = send if hosts match
false = send real referrer,
true = spoof referrer (use target URI as referrer)
0 = send full URI,
1 = scheme+host+port+path,
2 = scheme+host+port
Referrer processing is done in this order. So if XOriginPolicy is set to 2, then spoofSource and trimmingPolicy are useless if going from 1.mysite.com to 2.mysite.com, since no referrer is sent anyway.
The old setting, network.http.sendRefererHeader, is still there and can be used to completely disable referrer (by setting it to 0). Otherwise, to use the new settings described above, set it to 2 (default = always send referrer).
Note that even with the highest privacy & security settings, it seems that Tor Browser doesn’t touch those settings, so you’ll need to set them manually in Tor Browser too if you want to reduce referrer tracking.