I know one in Wintry Place; closer to the Northwest Passage side, there's an XP quoin that gives out a few hundred worth, but you need spinach/levitation to get it. I once got about 500 XP from it. :3
The [potentially] highest-yielding ones seem to have a respawn of up to an hour, so most players probably don't want to publish their favorite locations. ;) That said, the glitch strategy list is a pretty good start.
I just updated the GS post to include over 20 more locations (hopefully making it more than just a starting point ;)) and a neat "pro tip" which I totally didn't know about before.