I told my then-partner about the SO possibilities here, but I think we both felt uncomfortable with that. He found a site of his own but found it pretty depressing--mostly women with MTF partners, and a lot of drama and anger. My ex felt out of place there, but I guess it did him a little good. I think it was run by Helen Boyd. You might google her. He read one of her books, too, which I had bought for him--She's Not the Man I Married.
I tried to get him to go to the monthly SO meetings here in town. I guess there aren't many cities that have them. Anyway, he didn't go to any of those, either. If you have such a group in your area, give it a shot. If there isn't such a group, you might still meet SOs who can offer their experiences.
Are there any particular challenges that your partner faces (that you know of), or is it all just general understanding-what-it's-like-for-us stuff?