The shiniest stars at this year’s Mobile World Congress seemed to be the mobile app stores.

The pioneer, Apple Inc, led the way for other companies to come up with their own app stores. Although Apple did not attend the MWC, its Apple App Store was one of the main points of focus at the show.

The apps for mobile phones have been around for years, but Apple’s App Store were smart enough to offer an integrated, easy-to-use way to browse, buy, download, and install them on the iPhone 3G and iPod Touch.

The app stores of other big players of the mobile phone market will soon launch.

Nokia announced it plans to open its app store in May and will focus on location and social networking to fight competition. The app store will be compatible with all Nokia phones and the N97 will be preloaded with the service.

Nokia’s app store will show users relevant applications depending on location dynamics, it will also be able to show users what their friends bought and it changes its inventory based on the user’s location, said Niklas Savander, Nokia's executive vice president of services and software.

The other big player who plans to launch an app store of its own is Microsoft. The software giant will launch Windows Marketplace for Mobile which will feature a very large catalog due to the fact that there are at least 20,000 programs for Windows Mobile. The service will most likely be released sometime in the second half of this year.