Happens quite frquently when a bunch of users have access to SQL Server - LOL.
They could be using Query Analyzer and not properly choosing the DB they want, via the drop down box or by using a USE statement, to add table(s) to.
I would first try to identify who ownes the tables, maybe a user name is given. Then you must figure out if it was a user or a 3rd party app or tool that created these tables.
I would send out an E to all users who may use SQL Server that you are going to try and fix the issue. Then I would "RENAME" a table at a time to see what breaks and who hollers. If you are able to identify who ones it and what its purpose is, you could create another DB, move the table(s) and have your table owner rework their code to point to the new DB.
Just an idea!
Thanks
J. Kusch