One of the typical ways to improve scalability of high traffic website is to serve it contents from several web servers. This way all request for html pages will go to first sever and requests for media content will go to the second one allowing each server to perform better under high load. Amazon S3 offers you unlimited scalability and pay as you go model. You pay only for what actually is stored on your S3 account and pay only for the actual traffic.

Read more on how to set up Amazon S3 account