Amazon Web Services got the cloud infrastructure ball rolling four years ago, offering an Infrastructure-as-a-Service and killing the need for servers and, in-turn, data to be on-site. With that, dubbed Elastic Compute Cloud (EC2), Amazon set the table and in just a few years, dozens, if not hundreds, of companies clamored for a seat. While everyone does the infrastructure component a bit differently, the mission is clear: Cut costs, reduce space constraints, lower management overhead and offer scalable compute capacity on-demand at a figurative, and sometimes literal, flick of a switch.

Here are 20 cloud infrastructure vendors that are making the infrastructure game their own and altering the way IT is consumed.

Also, keep an eye out for the top 20 cloud platform, software and apps, storage and security vendors.

Amazon Web Services has become the one to beat in the cloud game, and Amazon EC2, its compute capacity play, set the standard for spinning up and taking down cloud capacity quickly and affordably with a pay-as-you-go model.

The communications giant’s wireless network may get a lot of guff, but there are no flies on AT&T’s cloud computing services. Its suite of Synaptic cloud offerings, which include Compute-as-a-Service and Storage-as-a- Service, comes with an SLA of 99.99 percent availability.

BlueLock comes at the cloud from a different way, offering cloud computing and managed services backed by VMware vCloud Datacenter Services. Its data centers are secure and SAS-70 Type II certified, so users know their cloud data is untouchable.

CA came out of its corner swinging for a knockout punch. With acquisitions over the past two years totaling more than $1 billion in cloud buys, CA has amassed a cloud army ready to battle all comers.

Want to build a cloud? Who you gonna call? It’s likely Cloudscaling. The company builds massive clouds for the world’s service providers, governments and enterprises via an open platform and with a keen eye on performance and economics.

While Datapipe leverages Amazon Web Services’ cloud infrastructure, it makes its cloud computing plays unique by adding managed services on top of Amazon EC2 to include monitoring, patching, change management, deployment and more, giving users tools to manage their cloud infrastructure.

ENKI may not be a household name, but the company is making waves with its roster of cloud computing services. And its PrimaCloud managed cloud computing service play offers scalable virtual private data centers with performance and reliability at their core.

From the great white North comes Enomaly, with its Elastic Computing Platform (ECP), which has been heralded as the first true Infrastructure-as-a- Service company. Enomaly’s IaaS play boasts massive scale, high reliability and an arsenal of features in a lightweight platform.

Private cloud infrastructure is the name of the game for Eucalyptus, which makes software that powers enterprise and government cloud computing environments. Eucalyptus offers an open-source way to efficiently use cloud capacity to beef up productivity and innovation.

GoGrid prides itself on being the biggest pure-play Infrastructure-as- a-Service company in the world. Its infrastructure lets businesses deploy and manage apps in the cloud platform within minutes and with a flexibility that separates it from the Johnny-comelatelies.

The big boys have been a bit slow to the cloud, but not HP. Its HP BladeSystem Matrix play lays the foundation for the private cloud and provisions infrastructure and apps while cutting ownership costs up to an estimated 56 percent.

The software stack is the cornerstone of Joyent’s cloud computing prowess. With a seven-year legacy in the cloud, Joyent developed the full software stack for its SmartDataCenter play, which it offers to service providers to deliver their own cloud services.

With a cache of managed dedicated hosting, ondemand grid/virtualization computing and Web services, Layered Tech’s infrastructure helps businesses break free of the shackles of hardware and get into the cloud with its secure IT infrastructure hosted in top-tier data centers.

With its infiniCloud play, Logicworks provides the ability to spin up and run virtual servers in minutes starting at 6 cents an hour. And if private cloud is your desire, Logicworks offers single-tenant VM solutions to build a private cloud.

Recently acquired by Time Warner Cable, NaviSite evolved from hosting to offering Managed Cloud Services for on-demand provisioning of IT services like apps, messaging, servers, storage and networks for enterprises. NaviSite promises usage-based billing, unrivaled SLAs and top-notch support.

OpSource has outgrown its traditional hosting roots with its public cloud IaaS, OpSource Cloud Hosting, a pay-as-you-go cloud infrastructure that OpSource guarantees has tight security, control, support for integration and, most importantly, 100 percent availability.

While formally known as Rackspace Hosting, Rackspace Cloud is taking over. And with Rackspace’s Cloud Servers infrastructure play, the top cloud dog of Texas is rivaling the major players with its select-asize, customizable IaaS backed by Rackspace’s own “fanatical support.”

Late last year, Savvis launched Savvis Symphony, its suite of enterprise-focused cloud solutions to let businesses break free from IT infrastructure. Savvis says its cloud infrastructure can reduce capital expense, improve service levels and keep enterprises at the forefront of cloud innovation.

When Verizon acquired Terremark, it vowed to let the business run as it had. That was smart. Terremark is a cloud infrastructure darling leveraging top-notch data centers to give governments and enterprises agility, scale and savings with its Enterprise Cloud offering.

Verizon makes it no secret that it wants the cloud and wants it now. With its Computing-as-a-Service play for the enterprise, which also has an SMB flavor, and its Terremark buy, Verizon is ahead of its competitors in the cloud game.