Wash out and reuse for parties or picnics, or put a hole in the bottom and use for growing seedlings. The save-a-cup scheme collects these cups for recycling.
Generally video cassettes are re-usable but if damaged or worn than they should be disposed of in the household bin. Unused cassettes can be donated to charity shops, see your local directory for details. They can be recycled in the book banks or clothes banks at your local Household Waste Recycling Centre or some Recycle Points.