BEWARE!I like this script overall, it's exactly what I was looking for but this will drop all snapshots on the instance of SQL Server, not just the ones related to the database you are snapshotting!
Note the lack of a DB name in the where clause for the following:
b.name AS orignal_database_name,
a.name AS snapshot_name
sys.databases AS a
sys.databases AS b ON a.source_database_id = b.database_id
ISNULL(a.source_database_id, 00000) <> 00000
Always review any code you download!