I trawl the ladyboy forums quite a bit and up till now I still hold this one - The Ladyboy Forums in high regard.
It's probably got the most content on our favourite subject although it's mainly on Thai ladyboys. In spite of that, a lot of info can be found here.
It's strength is sometimes its weakness since its got so much, and it can be pretty tricky finding an answer to a question without resorting to the search function.
Its got loads of pictures too and some useful non P4P "threads" as well.
An example of a good thread is this one "How to Treat a ladyboy" (found under the main thread of "News, views and ladyboys"). In this thread one board member stands out - Doug. Look out for his twenty something posts which were very thorough and informative.
I especially liked how he made an analogy of the Bangkok bars and Disneyland.
And also his reminder that unlike the film "Pretty Woman" we're not Richard Gere and nor is the ladyboy Julia Roberts. He also reminds us that the film was made by Touchstone Pictures which is owned by Disney.
Coincidentally one ladyboy (who loves Mickey Mouse) asked me where she could get the DVD on "Pretty Woman" last week. Really weird, these connections!
Anyway, long and short is, go see the forum. It's worth the time.