Sometimes I just need to backup all the dbs in a situation of moving the databases to another server.
The script below is both 2000 and 2005 compatible.
You might want to consider adding the COPY keyword if you are using the script in 2005.
This will deal with the problem of adhoc backups breaking backup chains

You can alter the script to include system databases

--------------------------CODE START----------------------------------
DECLARE @name VARCHAR(50) -- database name  
DECLARE @path VARCHAR(256) -- path for backup files  
DECLARE @fileName VARCHAR(256) -- filename for backup  
DECLARE @fileDate VARCHAR(20) -- used for file name

SET @path = 'C:\Backup\' 

SELECT @fileDate = CONVERT(VARCHAR(20),GETDATE(),112)

DECLARE db_cursor CURSOR FOR  
SELECT name 
FROM master.dbo.sysdatabases 
WHERE name NOT IN ('master','model','msdb','tempdb') 

OPEN db_cursor   
FETCH NEXT FROM db_cursor INTO @name   

WHILE @@FETCH_STATUS = 0   
BEGIN   
       SET @fileName = @path + @name + '_' + @fileDate + '.BAK'  
       BACKUP DATABASE @name TO DISK = @fileName 

       FETCH NEXT FROM db_cursor INTO @name   
END   

CLOSE db_cursor   
DEALLOCATE db_cursor
--------------------------CODE END-----------------------------------------------------

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