The best place for you to go is the fansite Central 101. They have a wealth of guides and amassed a mountain of info about the game we love so much. It's www.wizard101.com. There is also a link at the top of the message board page. I encourage you to explore the place.
By trainers you mean people who offer spells for training points, right?
If you are interested in making a plan for spending a particular character's training points, this tool is very helpful:
While it is primarily aimed at helping you make efficient use of your training points, each of the spells listed has a rollover tooltip that will tell you who and where the trainer is for that spell.