Cassette tapes should not be placed in your curbside recycling. The film tape is a "tangler" that gets wound around the processing machines at recycling facilities and can shut down a whole recycling operation.
There are some specialized plastics recyclers that may be wiling to accept the hard plastic outer shell and recycle it for a small fee. You would be required to remove the film first. The film tape cannot be recycled and must be disposed in the trash. Call Northcoast Recycling Specialist in Wickliffe (440.943.6968) or Secure IT Asset Disposition Services in Mentor (440.332.5005). You can also recycle cassette tapes via GreenDisk.