Forum Moderators: open
Because I'm not an amazon...
For that very reason, a monster caching service provider like Akamai is probably a feasible solution for you. And to be totally straight here, I have not heard of a service such as you are asking about - one that would facilitate getting your files into the cache of many ISPs.
But is web caching even the right place to look to help visitor access your pages faster? In other words, why have you chosen to look in this direction?
Are you in in a situation where your server is overloaded by requests? If so, I would think that most ISP caches would already be caching your files. But if that's not the case, perhaps you could take steps to tune your server, to optimize server-side compression, to further optimize all your images and html, etc.
Forgive me if you've already taken all those steps - I am asking to be sure the bases are all covered.