Except under the rules of the Alþing, the largest party has the first opportunity to form a majority government in coalition with other parties. By these results, the Independence Party with 30% of the votes gets first go. It was already in coalition with the Progressive Party (whose vote has roughly halved), so together they are still short of a majority.
The most likely outcome is that the new Regeneration Party, which split from Independence earlier this year will come into the coalition which would give a centre-right government a very small majority.