You've probably already heard by now about SQL Server 2005 Express Edition.  It's the next evolution of MSDE 2000. 

Here's the Top 10 Cool Things about SQL Server 2005 Express Edition:

1. Integrated common language runtime (CLR) support. Stored procedures and functions can be written using your favorite programming language.
2. Native XML support.
3. XCopy support for moving databases from one location to another.
4. Robust and reliable installation using either graphical user interface (GUI) or silent modes.
5. Automated servicing and patching.
6. Deep integration with Visual Studio to provide access to rich data controls like the DataGridView, DataNavigator, and DataConnector.
7. Support for databases up to 4GB.
8. Support for disconnected systems with SQL Server Service Broker and Replication.
9. SQL Server Express Manager, a new, easy-to-use database management and query analysis tool (available August 2004).
10. Easier deployment via Visual Studio ClickOnce (available in Beta 3).

I was going to wait to start looking at SQL Server 2005 when it becomes available for download in the next few weeks for the MSDN subscribers, but I'll probably install Express Edition tomorrow.  It allows you to easily upgrade to the other editions anyway.