There was a thread on this a little while ago - and it got me really interested in the subject. I was recommended this book
by another poster on here, which I bought and read and was blown away by. It takes you through the steps towards communicating with animals. One one hand, I felt like a crazy person while I was trying it, on the other hand - some of the results I got were absolutely eerie that I can't fathom any other plausible reason for why I got the answers I did.
I haven't had one out to speak with my horse - although I would LOVE to. I e-mailed one once and she never replied. I also haven't really attempted to hone my communicating "skills" for a while although I do plan to try.
Definitely an interesting subject, and I definitely believe that it can be done. Though I think that there are a LOT of phoneys out there.