Only about 10 ISVs have implemented the APIs today, Friedman said, but IBM expects to get many more. Vendors that signalled support Thursday include CFXWorks, which provides credit card processing for retailers; Cincom, which offers a business intelligence product; and InterNetworX, which sells enterprise resource planning software.

IBM expects most of the applications to be installed on premise, the model used by 90 percent of SMBs today, Friedman said, although some software will be offered as a service. The resellers will also be able to incorporate online backup services, he said. The remote management will usually be provided by the reseller.

IBM is setting up hundreds of "innovation centers" around the world where ISVs can go to add the APIs to their software. It is emphasizing the big role that partners will play, although in some cases customers will be able to download and install software themselves, Friedman said. Most customers will want the specialized help that local resellers can provide, he said.

Alienating resellers is the main risk for IBM, said Dan Olds, principal analyst at Gabriel Consulting Group, in Beaverton, Ore. Smaller resellers with little software expertise will benefit the most, he said, but bigger resellers may feel threatened that customers can now figure out what software they need online.

As a small business owner himself, Olds said the service sounds useful. "There are places you can search for applications, like Google, but you don't really get all those choices in one place," he said.

For companies with less than 50 employees, IBM will offer Lotus Foundations Start. It's a package of IBM's Lotus and Domino software that comes pre-installed on a server and is supposed to provide for all a small company's collaboration needs, including e-mail, security, directory services, backup, and recovery.

The product was unveiled at IBM's Lotusphere conference in January. It will be generally available by the end of June, priced starting from about $1,500, Friedman said. It will be the first of other "appliance servers" that IBM plans to release. IBM said it can be set up in 30 minutes and has "self managing" features to make it easy for small companies to use.

Big vendors have been trying for years to tap the SMB market, but have often struggled to meet the individual needs of small companies or come up with a viable business model. IBM said the global market is worth $500 billion, and called it its "largest opportunity for growth."