I read Seasons a Valdemar Anthology by Mercedes Lackey. The only thing wrong was it ended before we got see catch up with every story in her anthology series. I am sure she will have another one. These are stories by author authors she has invited to play in her world.
There are fan fiction sites that allow other writers to play in her universe. You can become a Herald by following the directions on http://www.dragonlordsnet.com/qo.htm I did it and am a teacher herald by the name of Herald Kit Katz. My companion’s name is Scholame (Skoo-la-may). I have written about Kit’s early upbringing on a horse farm and how she was chosen. It is quite a feat to get to Herald status. If you enjoy Mercedes Lackey and her Valdemar world, you might want to try to become a Herald.