Katla's the volcano 'next door' to Eyjafjallajoekull in Iceland, that erupted a few months ago. Since that one erupted, seismologists have been expecting Katla ( a much larger volcano) to erupt as well. It seems to be having a bit of a move about today, with 6 tremors in the area just today ~ quite a lot for one day. So just in case anything happens, the Icelandic Meterological Office (seismology department) is here and the webcam is here!
(Of course, it could just all be ice shifting/melting that's registered, so if it's that it'll be a case of, "move along; nothing to see here, go on with your lives people!")