Doug Kaye, who actually wrote a book on hosting, has been beta testing Amazon's CloudFront service--a high performance front end for Amazon S3. Doug's favorably impressed.

My calculations show that Kynetx would be able to put 80% of our bandwidth load on CloudFront (most static JS libraries) for $1.19 per day and if Doug's experience is typical get better performance to boot! Seems like a no-brainer to me given that we're paying several hundred dollars per month for a 750 Kbps circuit that I'd rather not upgrade for a while. Offloading 80% of that traffic would give us a lot of head room!