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.