I found this fantastic script of all places in the comment of someones blog post. It does a great job of laying out all the size detail for all the databases on your sql server.
SELECT DB_NAME(mf.database_id) AS databaseName
FROM sys.dm_io_virtual_file_stats(NULL, NULL) AS divfs
JOIN sys.master_files AS mf ON mf.database_id = divfs.database_id
AND mf.file_id = divfs.file_id
ORDER BY 3 DESC
A great follow on to this is a File Size Calculator to help make scene of the sizes, especially if you're working with large database (i.e., SharePoint
Thanks pinaldave and Jerry Hung.