I will also add a vote of confidence in HDDN. They are part of the NetDNA architecture but have a pay as you use it approach. We use them heavily and have had no problems (not an employee or anything, just an advocate after trying the others). Also, you can consider things like Amazon S3 or EC2 as well. It all depends on the file types and of course, the cost you are willing to absorb to achieve the results you need.