App stores focused on the needs of small and medium businesses (SMBs) seem to be proliferating quickly as cloud computing takes off. As discussed in What is an App Store, and Why Should You Care, a marquee SMB vendor, such as Google or Intuit, typically builds the app store and serve as the anchor tenant for it. The vendors that run the app stores typically have a strong brand and a large customer base. They woo developers to build and integrate complementary applications around their core applications and/or platforms, and in return, take a commission on sales.

Some of the SMB-focused app stores that have already launched include:

• Intuit's Workplace App Center, which provides a central location where small businesses can locate and try business applications that work with QuickBooks and with each other.
• Google Apps Marketplace, which offers Google users apps that integrate directly with Google Apps.
• Zoho's Marketplace, which provides applications that work with Zoho's solutions.
• Constant Contact Marketplace, which offers small businesses with applications that integrate with Constant Contact's email and marketing tools.
• NetSuite's SuiteApp.com, which features third-party solutions that integrate with NetSuite.

Plus, there are a few more SMB-centric app stores that I've been tipped off on that are in the works, but not yet announced. Of course, there are many app stores that aren't exclusively focused on SMBs, but feature plenty of apps relevant to SMB requirements, such Salesforce.com's AppExchange and Sugar CRM's SugarExchange. There's an even app store for Twitter. Not to mention all the marketplaces for mobile apps that work with different smart phones, from Apple's App Store to Google's Android Marketplace.

All of which leads me to wonder how this growing bubble of small business application marketplaces will sort out. Theoretically, app stores or marketplaces can help make it easier for users to find, try, evaluate and purchase applications. But things can get complicated if you use applications from several vendors that have a marketplace—for instance QuickBooks, Google Apps and Constant Contact.

Enter GetApp.com, which launched earlier this year. Unlike most app marketplaces, GetApp isn't organized around a core application or platform. Instead, GetApp positions itself as a neutral, "meta-marketplace" that is application and platform agnostic. Any app can be listed on GetApp (the vendor has about 600 listings to date). In fact, many applications that are listed on GetApp are also on different proprietary marketplaces.

To help address integration requirements, participating vendors provide GetApp with landing pages and documentation to verify integrations between their apps and other apps and marketplaces. User ratings, feedback and commentaries offer validation—or not—about how well these integrations actually work.

GetApps model for developers is also different. Basic listings are free, but developers can sign up for a premium, or more complete listing, with a pay-per-click model; the vendor doesnt take commissions based on application sales.

GetApp is a David among Goliaths, but will be interesting to watch. Potentially, GetApp can provide SMBs with more choice, transparency and neutrality than vendor-specific marketplaces—and give developers a new channel without requiring them to re-write their apps for another platform.

While its too early to predict how GetApp—or SMB app stores in general—will fare, the SMB Group will be tracking the marketplace area closely. In fact, we are asking respondents about their awareness, use and plans for marketplaces (among many other things!) in our 2010 SMB Routes to Market survey, which is fielding now.

It should be quite interesting to see if marketplaces can live up to their promise of becoming a new, powerful land very disruptive SMB solution channel. If you know of other SMB app stores that we should be taking a look at, please let me know!