[neilep (OP)]

I was wondering if there are any creatures that do not get cancer at all ?

If so, have their particular biology been investigated as to why ?

[another_someone]

I may be wrong, but I had some vague recollection that sharks did not get cancer.

I have no idea about insects (it would be difficult to imagine how a cancerous growth would grow inside an insect or arachnid).

[showmen]

sharks can get cancer but are better equipped to deal with it that us. I'm taking that from the following page:

http://www.elasmo-research.org/education/topics/p_bite_on_cancer.htm [nofollow]

[Bored chemist]

Dead animals don't get cancer. I rather suspect they are the only ones.

[MayoFlyFarmer]

actually, cancer is much more rare in almost all species compared to humans simply due to life span.  there are very few animals on earth that live anywhere near as long as we do, and since chances of cancers increase dramatically with age, it makes sense that an animal like a mouse that lives at maximum a couple years, doesn't really have to worry about it like a human who lives to be 80 does.  for this reason, i'm pretty sure that cancer is pretty much absent in the insect kingdom. 

the molecular mechanisms that govern tumorigenisis apply to pretty much all living things, so in a lab setting we are able to mutate animals  that ordinarilly wouldn't live long enough to get cancer so that the process speeds up and they do.  i've actually met the reseracher who was the first to be able to generate tumors in fruit-flies.  until he did it, people didn't think it would be able to happen; even under genetically modified lab conditions.