The most active volcano in “recent years” is Hekla. Hekla is thought to have had at least 20 eruptions since the settlement of Iceland (just before and around the year 900 AD). Hekla erupted 4 times in the 20th century. Last time Hekla erupted was the year 2000. We have now had 3 eruptions in a period of 2 years (Fimmvörðuháls, Eyjafjallajökull and Grímsvötn)! – The activity is therefore clearly increasing (which again is exciting ;))