UPDATE: for SQL 2008, this command has been depricated, and no longer works
If you need to do an immediate dump, without backing it up, here's a solution
(in my example, the name of the database is "log_db"
USE [master]
GO
USE [log_db]
ALTER DATABASE [log_db] SET RECOVERY SIMPLE WITH NO_WAIT
GO
-- This is the name of my "log" tran file - edit the database, click on "files" to get the name if it is not standard
DBCC SHRINKFILE ('Log_db_log' , 1)
GO
USE [master]
GO
ALTER DATABASE [log_db] SET RECOVERY FULL WITH NO_WAIT
GO