Colin Andrews is famous as a crop circle researcher, but apparently he doesn't just limit himself to investigating crop circles. He's also finding circles in the sky apparently. He posted on his blog yesterday (January 16th, 2010) a link to pictures of a strange circle that appeared on weather satellite images over Australian. As of today (January 17th, 2010), he is still investigating what caused the circle. He's considered the possibility that it might be caused by HAARP, but he is still waiting (as of today) for a response from the Australian government's weather bureau to see if they have an explanation. Of course, if it was HAARP, I doubt they would actually tell you that it was HAARP.
If you want to see if Andrews posts any updates on the circle, you can visit his blog here. You can also see pictures of the circle in question on his website here.