Each smartphone platform has its own app store, market, catalog, or world available to its users, and Android even has a couple other app stores in various states of rumor and reality. Two sources "with knowledge of the situation" have told the Financial Times that HTC will also be joining the app store game soon, although it's not clear which OS(es) their store would serve. When it comes to content to include in that store, HTC is reportedly planning to use both e-books and applications to fill their digital shelves.
HTC already has a pretty widely used Android skin and their own MobileMe-like service with HTCSense.com, so I suppose an app store seems like the next logical step. While many assume that HTC's store is destined for use with Android smartphones, there's also a possibility that Windows Phone 7 devices could be getting in on the fun. After all, they do have their HTC Hub on WP7 devices, so this "store" could just be an extension of the Hub, bringing together all of their apps available in one easy to find location.