Well, I don't actually hunt for them on purpose, but run into these by accident every time. Lately, the most places have been either right on, or next to, WBCQ's FREQ's.
http://www.wbcq.com/ Go figure... Other times have been around the 43M area from 6800kHz to 6995kHz. Usually around stupid-o'clock at night, like 06:00UTC, or so. Then, in the middle of the daytime, I've heard them around 11400kHz - 11995kHz, 13500kHz - 13995kHz, and 15040kHz - 15995kHz. So, sooner, or later, you'll stumble upon one, and most likely it will totally cover-up a station that you are trying to ID. (Um, yeah...)