host static files (images) to 3rd party host such as Amazon Cloud. Any modules can facilitate this? I want host all images files to the cloud, such as amazon s3. 

For example, when creating the node, uploaded automatically upload the files to the cloud, and all images path automatically point to the image stored in the cloud.  

Any modules facilitate the CDN transition? 

Thanks.
I would go with the CDN module, also checkout the AmazonS3 module.