This wonderful series has been the most fun resource I have ever used to learn a language. Even better it is free – if you go to their website and download the PDFs. The audio is free as well on the website. It is a sort of total immersion course, the books are completely in Icelandic, but these were formatted for the purpose of teaching the language in foreigners in Iceland. I still found them rather easy to use on my own at home here in the States. Also, it helps to have a Icelandic friend for the occasional help if you get stumped on an exercise. Below are some examples of the variety of content in the book:
Polyglot in Progress 