Big vendors like Oracle, IBM and Microsoft are all over the show floor at the Web 2.0 Expo this week, testimony that new Web-based technologies are making their way into the enterprise. But some attendees are still wondering, what is an enterprise mashup, and what will it do for me?

Enterprise mashups are lightweight applications that combine data from two or more sources to create something more valuable than the sum of their parts. They are often developed to solve a particular problem, implemented in days rather than months, and use standards like POX (plain old XML), Atom and RSS to make sharing and subscribing to them easy. They often combine internal and external sources of data.

That's according to John Musser of ProgrammableWeb, which maintains a catalog of public Web APIs (application programming interfaces) available to programmers for building mashups. It added 120 new APIs to its directory in the first three months of the year, up 150 percent from a year ago, and now has about 700 in total. "The slope is increasing fast," Musser said in a talk at the Web 2.0 Expo on Wednesday.

The mashup world is still immature, and there are hurdles for businesses that need to be addressed. Service-level agreements aren't always available, data quality is hard to assure and there are a host of security and regulatory issues to grapple with. But still some companies are taking the plunge.

Great Lakes Educational Loan Services used an external e-signature service from DocuSign to help it deal with the flood of loan requests it gets around this time each year. It combined the service with its loan application system on its Web site. In the first two months, 80 percent of its 72,000 applicants used e-signatures, which cut its costs in this area by 75 percent, Musser said.

Car maker Audi used to collect data manually from 20 sources, including its inventory system and competitors' Web sites, to do competitive analyses. Developers at the company used a data mashup tool from Kapow Technologies that now automates the process, and it took only four days to build.

Mashups began in the consumer world and are often traced back to HousingMaps.com, which combines property listings from the Craigslist bulletin board with Google Maps to make apartment hunting easier. The enterprise world lags behind the consumer world by 18 to 24 months, according to Musser, but mashup tools from vendors like IBM, Serena Software, Tibco Software, JackBe, Nexaweb and others are closing the gap.