Dan Rayburn, from Streaming Media, posted a great, comprehensive list of the CDN providers for video delivery. This list has been growing fairly quickly as new companies enter this space and Dan will be updating this list from time to time at cdnlist.com.
All of the companies on this list are what Dan would describe as "video delivery networks." In other words, these particular CDNs have servers that are dedicated to operating the delivery of video content. Some of these companies are in Beta and have just recently launched their service. Dan has also broken out those that are more peer to peer (P2P) based as well as some that are more regionally focused.
There are 40 companies in this list and it is a great resource. Thanks Dan for putting this together for all us video-philes.