I had a website tying messages-with gifts online around 2006. I notice that there are several patents dealing with this topic and I believe that I have written evidence that I considered the same processes that are now patented. I am wondering if I have something to sell to the patent holders?
Since you didn't apply for anything back then you do not have any particular rights. All you have is knowledge of something in the public domain that might be used to show someone's patent is invalid.
If you can document what you had, possibly by the wayback machine, and you studied the history of specific patents you might conclude you have killer prior art and have something valuable to anyone whom those patents are trying to be enforced against. I would think it is only valuable if it is dead-on and hard to find. One problem is it is hard to see how you demonstrate its value without giving away its value. It is only prior art if it is published (on the web will do). If it is published and findable they do not need you. After you approach them with a proposition backed up by evidence it will become very easy to find.
I'm not an attorney but I wonder if contacting a patent owner and saying "pay me or I will publicize my prior art" is considered proposing a legitimate business relationship or something underhanded.
As George White says, this might not constitute prior art, if it was not published in some way before the priority date.
However, it might be possible to make it serve as evidence of "obviousness to a person skilled in the art".
This is different from an argument against "novelty", and involves a different requirement of the patent statute. My impression is, however, that this is not as useful an argument as prior art would be - it is more difficult to argue.