Q: I am really furious with my neighbors.

They put their house on the market and never told me they were going to sell. Years ago we talked about the fact that my daughter and son-in-law loved their house and would like to buy it. They told me that if they were ever thinking of selling, they would let me know first. Do I have any recourse?
A: Unless you have a written agreement with your neighbors giving you the right of first refusal or right to purchase, you probably have no recourse.
It's very hard to hold someone to an unwritten agreement, although it has been done throught the courts if there is overwhelming evidence of some kind of intent. You would have to check with an attorney for a more detailed explanation. A conversation years ago probably doesn't qualify. They may have even forgotten it completely.
It's very common for people to say, "Oh, I just love your house. Let me know if you ever want to sell it because I would sure be interested." I hear this so often that I would call it "just being polite." Your neighbors may have heard that from several people over the years, so they didn't take it seriously.
I also find it's true that most of the people who express an interest would not seriously want to buy it, or can't afford, or aren't in a position to buy it when it becomes available. So, without a real commitment in the form of a letter or contract, I don't expect you can hold them to anything.
This is a good time to encourage everyone to try to work out some contractual arrangement on property that seriously interests you. It can be recorded on the deed to the property, which means that your interest must be addressed before anyone else can buy it. In most cases, keep in mind that you will have to be willing to pay market price for the property.