Well tossing them into the garbage to fill up landfills are never a good idea. If these are movies consider donating them to area organizations who will watch them. Shelters, day cares, or senior citizen areas are always in need.
If these are tapes you have recorded things on consider listing them on freecycle or craigslist for free. A lot of people would be interested in taking these off your hands.
Another option is a company called Green disk. They will dispose of this for 6.95 per 20 pounds. Here is a link: http://www.greendisk.com/gdsite/pack-ITservices.aspx