We currently use Edgecast through Speedyrails. Back when I did my research they were both fast and very cost-effective.
I haven't looked in a while, but now we need SSL on our assets as well.
I reached out to our current provider and they want a setup fee and something like 260 USD per host per month (we use multiple hosts currently).
I looked at AWS Cloudfront and it seems the most cost affective way to get SSL, but it's not a custom domain then (e.g. cdn.example.org), which I could live with.
Has any else researched this lately and has any providers to get in touch with - can be resellers or direct buys. I'm not looking for a bargain, I just want to get an idea what these things cost.
Edit, 2012-08-23: Must have is custom origin. E.g. I don't want to manually upload files somewhere else. Edgecast and Cloudfront both support this.