GIS in the cloud?

I'm post to get this thread going.

I worked at Esri for four years and I am somewhat aware of how they are using Amazon's infrastructure to support using ArcGIS in the cloud. I am interested in learning more about this, but for the Science Cloud Summer School I am more interested in learning what I need to know to perform spatial analysis using open source GIS tools like GDAL (http://www.gdal.org/) and OGR (http://www.gdal.org/ogr/) and/or sing R.

I'm using pretty simple datasets — basically just shapefiles of relatively simple polygons — but they cover almost the entire world in spatial extent and I'd like to perform analysis at a fairly high spatial resolution.

Looking forward to learning more!