On the very low end of that spectrum of managed/dedicated server providers would be Rackspace but I have heard it may not be as good there any more. On the high end of the spectrum would be IBM but that is very expensive. In between are various managed server providers. Just look for managed hosting and what you would actually want to research is who their customers are. Or look at it the other way around. Find medium sized companies and research who their managed hosting providers are.
Another method would be to look at colocation providers. They can give you blocks of IP space. On the low end would be Hurricane Electric if you are on the west coast. A step up from there would be Sonic. There are a myriad of colocation providers that scale up in price from there. If you wanted a presence in many locations then Equinix may be a good option though they can be expensive when you are first starting out. All of these providers have partnerships with network providers and can help get you peering arrangements, address space and much more.
Another method would be to look at colocation providers. They can give you blocks of IP space. On the low end would be Hurricane Electric if you are on the west coast. A step up from there would be Sonic. There are a myriad of colocation providers that scale up in price from there. If you wanted a presence in many locations then Equinix may be a good option though they can be expensive when you are first starting out. All of these providers have partnerships with network providers and can help get you peering arrangements, address space and much more.