AppDirect, a company that offers white-label cloud-based app stores, has today announced $8.5 million in funding to ride the wave of interest in cloud services and continue its expansion in partnership with third parties. And today the company also announced a new customer in that strategy: Rackspace, which has launched the Rackspace Cloud Tools Marketplace, an online store for cloud-based software and services to more than 180,000 Rackspace customers worldwide. The Series A round was led by iNovia Capital with participation from existing investors, and comes on the back of a seed round of $3.25 million raised last year. Cloud services have been steadily picking up momentum in the enterprise -- Gartner just the other week noted that they will be the fastest growing segment of enterprise services in the years ahead and will total $109 billion this year. Up to now, AppDirect has been winning some good deals in this segment among companies that are already serving enterprises with cloud-based storage, and now want to begin offering more value-added services on top of that -- partly to differentiate from their competitors, but also for convenience. In addition to Rackspace, AppDirect also counts Deutsche Telekom, Bell Canada and Appcelerator among its customers. In total, there are some six million end users worldwide accessing apps through its' cloud platform, which acts as a kind of one-stop shop for cloud-based software like Google Apps, DocuSign, New Relic, and SendGrid. Rackspace's Cloud Tools Marketplace, the companies say, will include some 100 applications for customers to use: they include billing and file management solutions, as well as online backup applications and a range of business-critical applications have been fully integrated into the marketplace, including New Relic, SendGrid and Standing Cloud. AppDirect also runs the billing system in the backend to manage the buying process and can authenticate users of multiple apps with a single, encrypted sign-on. The fact that end users do not have to "shop around" for apps and can get them from a single marketplace is already a compelling idea, but there is also potential for AppDirect to work directly with large enterprises to create app stores for their employees to access. Daniel Saks, president and co-CEO of AppDirect, notes that the funding will in part be used to develop new services. "We're going to have a lot of exciting news to announce over the next few months, from developer engagement activities to new partnerships," he says. "This funding announcement is just the first in a long string of successes to come."