I want to share a use for egg rings that has come in handy for me quite a few times. I'll preface the article by saying that I spent a few summers up in Vermont as a wilderness camp counselor and had to cook every meal over the fire those summers, so I have some good experience.
With that said if you ever find yourself cooking over a fire one of the handiest tools to have is an egg ring. They are light and easy to carry, so even if you are backpacking it isn't a problem to bring along. The reason they are so helpful is this: When you are cooking over a fire or camp stove you are almost always cooking multiple things in the same, small pan. Others might say that a true outdoorsman does not care if his food runs together but I would say it is not pleasant to have young campers complaining that their food is one big blob.
I digress, for there are certainly other reasons to mention. For instance, the egg ring can also be quite handy by creating an egg or pancake or any other liquid that becomes firm when it cooks, into a very convenient shape. Often there is no dining room table to eat at along the hiking trail so having things that are easy to hold and eat with your hands is nice. Also, if you pack certain foods into the egg ring you can create a more convenient meal with any food. For instance, if you put a flour and water mixture into the ring you can dump anything else (corn, dried fruit, peas, nuts, etc) in there and end up with a meal that you can carry in one hand.
Finally, if you are not concerned about getting a cooking utensil dirty there are some other uses as well. I would recommend filing the top edge of the ring into a sharp surface and using it for hand fishing. Many people try to spear small fish with a single point object, but I have had much better success with something that covers more area. Keep in mind, you will probably only pin the fish against the bottom of the stream and will then have to grab it. One last use is to build it into your fire pit. Typically it is good to leave an air hole on each side or your fire pit wall and an easy way to do this is just to build on top of your egg rings and then remove them. If you are using mud or rocks the structure should hold up when it's complete if you take the egg rings out.