AWS blog posts an entry they have added the capability to two new "high-cpu" instance types.
Amazon EC2 users now have access to a pair of new "High-CPU" instance types. The new instance types have proportionally more CPU power than memory, and are suitable for CPU-intensive applications. Here's what's now available:
The High-CPU Medium Instance is billed at $0.20 (20 cents) per hour. It features 1.7 GB of memory, 5 EC2 Compute Units (2 virtual cores with 2.5 EC2 Compute Units Each), and 350 GB of instance storage, all on a 32-bit platform.
The High-CPU Extra Large Instance is billed at $0.80 (80 cents) per hour. It features 7 GB of memory, 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each), and 1,690 GB of instance storage, all on a 64-bit platform.
Behind the scenes amazon uses Citrix Xen for virtualization.
Amazon Elastic Compute Cloud, also known as "EC2", is a commercial web service which allows paying customers to rent computers to run computer applications on. EC2 allows scalable deployment of applications by providing a web services interface through which customers can request an arbitrary number of Virtual Machines, i.e. server instances, on which they can load any software of their choice. Current users are able to create, launch, and terminate server instances on demand, hence the term "elastic". The Amazon implementation allows server instances to be created in zones that are insulated from correlated failures.. EC2 is one of several Web Services provided by Amazon.com under the blanket term Amazon Web Services (AWS).
EC2 uses Xen Virtualization. Each virtual machine, called an instance, is a virtual private server and can be one of three sizes; small, large or extra large. Instances are sized based on EC2 Compute Units which is the equivalent CPU capacity of physical hardware.
1 EC2 Compute Unit equals 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor. The three available Instance sizes are sized as follows:
The small instance (default) is the "equivalent of a system with 1.7 GB of memory, 1 EC2 Compute Unit (1 virtual core with 1 EC2 Compute Unit), 160 GB of instance storage, 32-bit platform " 
The large instance is the "equivalent of a system with 7.5 GB of memory, 4 EC2 Compute Units (2 virtual cores with 2 EC2 Compute Units each), 850 GB of instance storage, 64-bit platform"
Extra Large Instance
The extra large instance is the "equivalent of a system with 15 GB of memory, 8 EC2 Compute Units (4 virtual cores with 2 EC2 Compute Units each), 1690 GB of instance storage, 64-bit platform."
Wouldn't it be great if enterprise IT was run this way. Amazon is figuring out how to sell compute better than anyone else, and that is their business as a retailer.