A free tool for managing your MSDE or SQL Server (MSSQL) databases:
Visendo SQL-Admin:
http://www.visendo.com/en/download.aspx
It does most stuff relatively well. Add/remove database, attach/detach, browse data. Unfortunately, no visual view builder. It's not quite as capable as the SQL administrative tools included by Microsoft with SQL Server, but it's sufficient. And the price of 0 is good.
Another freeware MSDE manager:
http://www.asql.biz/DbaMgr/DownLoad2k.shtm
Microsoft, themselves, provides a Web interface (which can run locally with an included mini-web server):
http://www.microsoft.com/downloads/details.aspx?FamilyID=C039A798-C57A-419E-ACBC-2A332CB7F959&displaylang=en