iMountain

They offer a seriously interesting range of hosting packages all of which rely on some kind of cluster technology. Rather than have a single web server assigned to your site, this cluster approach lets traffic bursts be spread across multiple servers. Additionally they offer cache technology such as memcache to help relieve traffic load for web technology that can utilize memcache. The hosting features are comprehensive.

They operate their own data center with their own solar power plant to power the data center.