We've release the first CTP of SQL Server Everywhere Edition. If you aren't familiar with SQL Server Everywhere Edition, here's the description from http://www.microsoft.com/Sql/Everywhere:
"Microsoft SQL Server 2005 Everywhere Edition offers essential relational database functionality in a compact footprint ideal for embedding in mobile and desktop applications including a new generation of occasionally connected dynamic applications.
Sharing a familiar SQL syntax and common ADO.NET programming model with other SQL Server Editions, and management via SQL Server 2005 Management Studio, SQL Server Everywhere Edition allows developers and administrators to apply their existing skills and be immediately productive.
In addition, SQL Server Everywhere Edition enables scale-up of an application, either via a robust synchronization with other SQL Server Editions, or by moving to a higher edition of SQL Server. SQL Server Everywhere Edition allows you to extend your integrated data management platform deeper into your enterprise and into your mobile workforce."
It's an ideal database for Smart Clients. My favorite feature is the ClickOnce integration. Steve Lasker has a nice blog entry explaining what's in the release and a basic walkthrough here. The Sql Server Everywhere (formerly SQL Server Mobile) team blog is http://blogs.msdn.com/sqlmobile/ (they will change the blog url eventually). You can download the Microsoft SQL Server 2005 Everywhere Edition CTP here.