I use Amazon’s S3 service to serve images for this Web site. It’s a great service, especially for high volume site (don’t I wish) because it scales automatically. It’s also a pay as you go service meaning you only pay for what you use. Amazon now has a Dashboard that shows the current and historical status of these services.
Rumor has it that Amazon will make more money selling these services than from their mainline merchandise business within a couple years.