Yes. There is.
SÃ*minn is the best network. 3G coverage even in areas where nobody seems to be alive. Vodafone is close behind. Both are good if you want to go the ring road.
Nova is the 3rd network. Much cheaper, but only good if you stay in the Reykjavik metro area.
Here is a survey of starter packs and data options. To call to the US, you can choose any VoIP provider.
http://prepaid-data-sim-card.wikia.com/wiki/Iceland