Add a tag or attribute to a user or computer

Ability to add tags to user or computer to be able to group them more precisely. Currently a user can only be a member of one company. If you could add a "tag" or a "attribute" to a user or a computer we can group them better. Have a dropdown of the tags like the company when sorting items. Examples - East, West, 500 location, SQL server, Domain Controller, Video Server, Sritical Server