SQLLite is awesome. And by far the one I trust most for stability.
However it cannot function over windows shares. This means that there really isn't much of a distributed system available.
So I was reviewing the "FREE" options. This came up:
Will review the free ones with good .NET support.
These in particular:
Scrimore is highly respected (i knew that before).
But EffiProz is improving (previously i remember it's codeplex page http://effiproz.codeplex.com/ now its http://www.effiproz.com/Downloads.aspx . Doesn't mention beta on the new page)
Its is going to be about performance and how easy it is to change from embedded to client / server.