iPlant Atmosphere is free to use for members of the research community, with generous monthly allocations that get automatically refreshed. Any special requests made for more compute time will be evaluated on a case-by-case basis.
I've been meaning to give the Amazon Elastic Compute Cloud a go but haven't had the chance yet. It has been advertised as free, as long as you don't overuse the free quota (http://aws.amazon.com/ec2/).
Do you mean cloud computing (or similar) resources that you can access for free and that is off-site? If you are at a University and since I see you are in Canada look into Compute Canada resources. They are clusters in different areas of the country that you (and your supervisor) can apply for access too. Calcul-Quebec probably has the best and biggest resources as part of the network, and you aren;t restricted by region for which resources you apply for access too.