How to reference the results of Kaggle and other similar competitions in an academic paper?
I have cited these resources before in academic work. Usually I cite them in a general and holistic way, not a specific way.


  Several of the results presented in this paper were inspired by the discussion and resources on the Iowa Housing Project contest on Kaggle.com [citation with URL]. These resources were invaluable in determining a new approach to fitting a random forest model as found in this work.


I would avoid citing specific solutions, as these tend to be transient and informal. Such generalities as the one I've given above provide you with a blanket cover for any code which might resemble code on Kaggle. Citations are usually done for two main purposes:


Provide attribution and recognition for a researcher.
Provide insight into the research processes of the author of the paper. 


The anonymity and changing nature of resources on a site like Kaggle make it very hard to track citations attempting to accomplish the first purpose. Thus a general citation will at least give insight into how you wrote the paper and what though processes you went through.