Nielsen has released a new mobile application report and its findings showcase not only the increase in smartphone usage, but also what applications are most popular. For its report, Nielsen surveyed more than 4,200 people who had downloaded a mobile application in the last 30 days.

The survey really highlights just how much smartphone ownership trails traditional feature phone ownership, at least in the U.S. Nielsen’s study shows that 21% of American wireless subscribers have smartphones.

Still, even non-smartphone users have heavily embraced mobile apps. Nielsen’s survey indicates that the average number of apps that a feature phone user has on his or her device is 10, while the average number of apps a smartphone user has is 22.

Broken down even further, the average number of installed apps based on smartphone OS looks like this:

• BlackBerry: 10
• iPhone: 37
• Android: 22
• Palm: 14
• Windows Mobile: 13

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Most Popular Smartphone Apps

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While the specific applications vary from platform to platform, the most popular apps across smartphones were pretty consistent in this report: Maps, weather, Facebook and music all had strong showings.

Check out this chart which breaks down the five most popular apps by smartphone OS:

It’s interesting to see just how much Facebook dominates the mobile app space; it’s one of the top five apps on each of the platforms highlighted. Still, Nielsen notes that broken down by demographic, MySpace is still very popular among teens and that LinkedIn is strong in the 25-44 demographic.

DEMO Spring 2010 officially kicks off on Monday morning, but at the welcome reception earlier tonight, we got a chance to meet with some of the companies that will be presenting their products over the next two days.

One of those companies is Zerista, which is a tool that lets groups, clubs, teams and organizations build their own mobile optimized applications. Think of it as a private Facebook/Foursquare/Twitter mash-up.

What we like about Zerista is that it can integrate with your existing social networks, while also creating a web-based (and mobile optimized) network for communicating news, sharing messages, doing mobile check-in and even collecting payments for tickets or dues.

You create the application and provide details about who your members are, any custom maps you want to include (that can replace generic Google Maps) and any activity calendars or events. You can also select what type of privacy and sharing options you want — so you can designate if communication shared in the group is also shared outside to other networks or to the public at large.

While some might not see the point in building a custom social app, we can already think of several situations that would really benefit from such a system. For instance, I was in a sorority in college and trying to track down meetings, locations for philanthropy events — not to mention collecting dues — was something that even in the early Facebook era wasn’t well optimized.

Having a mobile-accessible network that can be private — but also integrate with large public networks would make that management process less complicated and also make it easier for group members to find out what’s going on and communicate with one another. Zerista is open for beta now.