there's not a lot of work in long haul trucking simply because the country is so small, but I know one truck driver who owns his rig and moves large building elements around (like huge concrete pipe sections).
A search for "bílstjóri óskast" (truck driver wanted) on the net shows a lot of ads that are mostly rather old. Still, you can get an idea of who might hire. Places like Eimskip or Samskip (the "big" cargo ship companies) need to transport domestically, there are various store chains like Hagkaúp and Bónus and Krónan that have to move goods.
you can also check out these companies that are somehow involved in goods transport according to the yellow pages:
http://ja.is/?q2=flutningar&q=flutning
As I've mentioned in other job-related threads, Iceland's job market is VERY much based on who you know, and many jobs that are open aren't advertised at all. My company, for example, has hired several people recently and all of them were hired via word of mouth. If you can get to know one or two people in Iceland (perhaps call around with teh intention of visiting some companies, then follow up with a visit to the country) you will probably have better luck than trying to find a job from afar.