Organize a Swap Meet
If you have a field that's being left fallow, consider using it on the weekend for a large swap meet. People love to wander around a field to see what kind of bargains they can find.
Charge the vendors a small fee, maybe $7 per car and $15 per truck (depending on your area and demand). If you stick with it, this could develop into a profitable weekend venture that can be moved to a different field each season. Depending on where you live, you could even have the swap meet year-round.
Ensure you have an area for parking off road for those looking to buy. Signs on the street and even an ad in the newspaper will bring people flocking to your field for potential bargains. Once your swap meet (car boot sale in the UK) gets known, advertising won't be necessary as word of mouth is your best advertisement.