I'm using http://maxcdn.com/ - it seemed one of the cheaper ones at the time, and it's worked well for us.

I use maxcdn for the-hobbit-movie.com (W3 Total Cache) and recommend it too.

I use maxcdn for static content (css/js/images) and Amazon Cloudfront for videos.

We use Limelight which is much cheaper than Cloudfront or Rackspace at 95th % > 1gbit. They are also well dispersed in the world minus South America.

Akamai is still by far the best at prices roughly equal to CloudFront and Rackspace (at 95th % > 1gbit).

CDNetworks is still the best in Korea. ChinaCache is the best in China (gov't owned probably..)

EdgeCast most likely the best in South America.

Australia is tough. Akamai still the best.

Amazon's CloudFront. I use it for both a WordPress blog (via the W3 Total Cache plug-in) and for high-definition video streaming to clients. Shockingly simple to setup and use. Cheap too.

I've been using Rackspace Cloud for ~6 months. No complaints so far.

Rackspace+Akamai for www.9Slides.com

We use Google App Engine as a CDN.