"What we see happening is [companies like] WebEx Connect, Salesforce.com, Microsoft and Google are trying to fence in their little area of the cloud," he said, describing the scenario as "you sign into Salesforce.com in the morning and stay there all day."

However, not everyone is going to be on the same platform, and people will have to be able to interact seamlessly with other files created on different cloud environments. "We're the agnostic that sits in the middle," he said. "You can view and edit your documents in eXpresso but be inside any of those platforms."

EXpresso recently made its Excel service available for Salesforce.com, so users of the online customer relationship management service can "toggle seamlessly" between Salesforce data and Excel spreadsheets to share customer information between the two without leaving the Salesforce.com environment, Langan said.

EXpresso doesn't have its own data center; rather, the company hosts its service on Oppsource. The basic eXpresso service is available free and is used by about 8,000 customers, Langan said. EXpresso pro, which costs US$15 a month or $79 for a yearly subscription, has about 400 customers.

EXpresso has about 10 employees in Palo Alto, while development for the product is done by a staff of 16 in Vietnam, he said. EXpresso CTO Huy Nguyen is Vietnamese-American and set up the development team overseas.