For an overview of SQL Server features, see this article. On top of the evaluation edition, Microsoft offers a free SQL Sever 2012 Express edition for lightweight use, which can be downloaded here.

SQL Server 2012, Microsoft's flagship database product, is officially out. What's actually available, though, is a bit of a mystery. Microsoft describes it as being at the "general availability" stage ...

SQL Server 2005 Express Edition will replace Microsoft SQL Server Desktop Engine as the software maker's lightweight database offering of choice.