Who uses the service: Web developers and software-as-a-service providers such as Zapproved, which uses Mosso to deliver an online productivity tool.~~

Company name: RightScale 

Founded: 2006

Location: Santa Barbara, Calif.

Cloud offering: The RightScale Platform, software-as-a-service that helps customers manage the IT processes they have outsourced to cloud providers such as Amazon and GoGrid. RightScale helps customers build and clone virtual servers for the cloud, performs load balancing in response to changing needs, automates storage backups, and offers monitoring and error reporting.

Why we're watching it: Because for all of the cloud's promises of simplicity, deploying new virtual servers and applications in the cloud requires work on the part of the IT department, particularly if a customer is using multiple cloud services. RightScale is automating the grunt work required to use the cloud most effectively.

CEO: Michael Crandell, RightScale co-founder who was held executive positions at software-as-a-service companies including eFax and Celebros.

How RightScale got its start: Two of RightScale's three founders come from Citrix Online, including CTO Thorsten von Eicken, who decided that software providers shouldn't be burdened with the enormous task of building and maintaining data centers. Building data centers should be for "other people who have a core competency in that," he says. "I build SaaS services and there's no reason to go out and build a data center again."

Who uses the service: Social networking vendors and other companies that need help managing cloud-based servers, including ShareThis, TagCow, DoInk, and iWidgets.

Company name: Salesforce.com 

Founded: 1999

Location: San Francisco

Cloud offering: Salesforce.com's flagship is a set of CRM tools including salesforce automation, analytics, marketing and social networking tools. A second major offering is Force.com, a platform for building Web applications and hosting them on the Salesforce infrastructure.

Why we're watching it: Salesforce.com helped pioneer the software-as-a-service market, which has now been lumped into the umbrella term "cloud computing." With Force.com, Salesforce is moving beyond SaaS into the platform-as-a-service market, which could revolutionize the way businesses build and deliver applications to end users and customers.

CEO: Marc Benioff, also the founder and chairman of Salesforce.com, spent 13 years at Oracle in a variety of executive, sales and product development roles.

How Salesforce.com got its start: Benioff founded Salesforce.com with the goal of creating an information management service that could replace traditional business software technology, the company says. Initial funding was provided by investors including Oracle CEO Larry Ellison.

Who uses the service: 55,400 customers in many industries including financial services, communications and media, energy, healthcare and retail.