I came across this talk on using MongoDB with Amazon Web Services. It is focused around how you can achieve simplicity, stability and scalability through using the two together. For anyone interested in getting a feel for how you go about using MongoDB on AWS and why they are a good fit it is well worth a look.
AWS also has a great Whitepaper which covers best practice. It takes you through installing MongoDB, setting up replica sets and sharding, backups, monitoring, security etc.