I An Web

The Amazon service is very reliable and many people are using it but it can become expensive very quickly but as many use it for small projects people find it pretty cheap.
 
The S3 option as @BlueDreamer suggested could also be a possible Amazon solution, but can handle your needs just depends what is going to be done with files.
 
You can easily get a hosting company that does managed hosting to do all the work for you and setup a clustered setup. Some of our clients who have the same sort of requirements run multiply low end CPU servers with very large RAID harddrives and then the front end (plus admin area) of the website manages the file locations. For instance fileserver1.yourdomain.com / fileserver2.yourdomain.com and so on. Just an idea for you as this might work out easier to develop for and might also be a cheaper option.
 
With CDN's large files are harder to work with on a true CDN network as you need large amounts of disk space in multiply countries. If you went with the low CPU servers you could get servers in the US and some in UK/EU and mirror between them.
 
Hope I have helped but let me know if you have any questions and I will be more than assist

Pretty simple I believe:
Create a container. Add a a list of links to the container. Style the links appropriately. Use the rotate css property to style rotate the container and the links.  
As for the growing effect when you hover over the link, I imagine that is done with javascript, just by increasing the width of the link.
 
Ian.