I use SQL Sever Developers’ Edition, but I have also experimented with MSDE.  As a developer, I think it’s important to be familiar with all the tools (I also use Web Matrix from time to time).  This free download from Microsoft makes working with MSDE so easy!  For those who may not have access to SQL Server, this tool makes MSDE very accessible.  You must have either IIS or Cassini running as your web server(Cassini comes with Web Matrix – free).