Microsoft has established Xbox LIVE as a feature that only top-quality, non-clone games can hold. Obviously most games aren't going to make that cut -- which leaves them without a central leader board and achievement system. Luckily for developers, OpenXLive has already set out to correct that.
OpenXLive connects gamers on Windows Phone 7 with a social network (SNS) platform, and enables mobile game developers to add social networking features in games with minimal development efforts, including friends, leaderboards, forum, and more. OpenXLive was developed by Fulcrum Mobile Network, Inc. Similar platforms include OpenFeint and Plus+, both of which run on iOS devices.
OpenXLive, which is basically a clone of Xbox Live, without the Avatars and Xbox integration supports Silverlight-based games, custom user pictures and achievements. The system now has 28,000+ users and is incorporated into 12 games already, making it quite a viable system for indie developers and others that are finding Microsoft's official Xbox LIVE certification hard to attain. At least 40 more games are said to be in development for the system.
More Info: OpenXLive