If you have a public domain or non-proprietary data set that you think is useful and interesting to the AWS community, please submit a request below and the AWS team will review your submission and get back to you. Typically the data sets in the repository are between 1 GB to 1 TB in size (based on the Amazon EBS volume limit), but we can work with you to host larger data sets as well. You must have the right to make the data freely available.
Given that Amazon is a gold sponsor at the Esri Dev Summit, maybe this would be a good time for the community to recommend data sets for Amazon to put in their cloud.
Having the data on Amazon allows fast access by things like Server Object Extensions and geoprocessing services running on EC2.
Currently I just see 3 datasets for geography.
Update I dropped by Amazon's booth at the Dev Summit and spoke a bit with an AWS rep. He said they are still sorting out how they will keep public dataset current. He said there has been a lot of interest from the Human Genome community. He said to expect something in last half of 2011 regarding changes to community data sets that will make it easier for GIS.
I also visited with Microsoft. While Azure looks promising, it doesn't look like you'd be able to do server-side geometric network traversal, as you would with AWS.