Topics which I read based on the previous forum discussions
Amazon DynamoDB January 2016 Day at the SF Loft - DynamoDB Design Patterns and Best Practices - https://www.youtube.com/watch?v=PDQ3jbDyTQ4
AWS re:Invent 2015 | (NET201) VPC Fundamentals and Connectivity Options - https://www.youtube.com/watch?v=5_bQ6Dgk6k8
Optimising S3 Key (File) names for heavy load (http://docs.aws.amazon.com/AmazonS3/latest/dev/request-rate-perf-considerations.html)
Optimising DynamoDB operations (http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScanGuidelines.html)
ELB and session cookies (http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/elb-sticky-sessions.html)
Topics i covered on my own and found to be of some value in the exam
Journey Through the Cloud - Security Best Practices (I took this instead of going through the AWS Security Whitepaper) - https://www.youtube.com/watch?v=rXPyGDWKHIo
Advanced Security Best Practices Masterclass - https://www.youtube.com/watch?v=zU1x5SfKEzs
Know the available SDKs - https://aws.amazon.com/tools
Also - make sure you understand each and every question in the sample questions provided by AWS. i thoroughly worked them out and found that 9 out of 10 questions in the sample paper come in the main exam. - http://awstrainingandcertification.s3.amazonaws.com/production/AWScertifieddeveloperassociateexamsample.pdf
Also - if you have time, go through the premium support FAQs. https://aws.amazon.com/premiumsupport/knowledge-center/. these are typical scenario questions which address scenarios when something wrong happens in AWS and how to rectify them. This will give you a better understanding of the issues that you might come across while working on AWS.
Finally, All the best to everyone who is going to take the CDA exam!