You explicitly mention three services in your question title: EC2, RDS and EBS.
If they’re the three services you’re interested in, then yes, very easily.
EC2 + EBS are pretty much the same thing, EBS is simply a persistent storage extension to EC2, and RDS is a full MySQL database – you should be able to get those three services running together very easily.
If you were looking to extend to some of the other AWS products, S3 is very easy to implement on WordPress for file uploads – check some of these plugins.
SimpleDB, however, has very limited usefulness to us without a rewrite of how WordPress reads and writes to the database. There is an article by Amazon on how to create a plugin which adds tagging functionality that uses SimpleDB as the storage, but that is as much as I could find regarding the use of SimpleDB with WordPress.