The folks over at Cloudcraft have created a great resource to easily build and manage architecture diagrams. You can drag and drop, edit and manipulate icons for all AWS services, and add text, visual aids and even Font Awesome icons.
It's also a free service.
As a quick example below is how this site, statically hosted in an S3 bucket, served through CloudFront and using API Gateway + Lambda + SES to handle dynamic functionality (processing a contact form) would be modeled:
This is an incredibly simple example that only scratches the surface of its capabilty but gives a good idea of the output.