I know Amazon has support for .NET and Java.
There is now an official AWS SDK for Node.js, see the introductory post AWS SDK for Node.js - Now Available in Preview Form for details, here are the initially supported services:
The SDK supports Amazon S3, Amazon EC2, Amazon DynamoDB, and the Amazon Simple Workflow Service, with support for additional services on the drawing board. [emphasis mine]
Wantworthy has implemented a Node.js module for accessing Amazon DynamoDB a week after its launch date, thus covering 2) as well, see dynode:
Dynode is designed to be a simple and easy way to work with Amazon's DynamoDB service. Amazon's http api is complicated and non obvious how to interact with it. This client aims to offer a simplified more obvious way of working with DynamoDB, but without getting in your way or limiting what you can do with DynamoDB.
Peng Xie has implemented a Node.js module for accessing Amazon DynamoDB at its launch date basically, thus covering 2) already, see dynamoDB:
DynamoDB uses JSON for communication. [...] This module wraps up the request and takes care of authentication. The user will be responsible for crafting the request and consuming the result.
If you don't use one of the AWS SDKs, you can perform Amazon DynamoDB operations over HTTP using the POST request method. The POST method requires you to specify the operation in the header of the request and provide the data for the operation in JSON format in the body of the request.