I had a service dog. He passed away last year. Loki was great. I trained him myself with the help of a dog training program out here called Pawsabilities. They offer training from everything from basic obedience to agility to service dogs (service dog training is free with obedience).
Loki was part Austrailian Cattle Dog and part pit bull. He was a stray who was thrown out of a car on the freeway. Having him was a blessing. At that time I could barely leave my house. The panic attacks were worse because I am deaf in my left ear. I could not hear people walk up behind me or beside me. It really freaked me out.
He was the coolest dog. I always knew I was safe with him. He would always let me know when I was going to have a panic attack and he could usually pull me out of one. If not he could be counted on to give me an excuse to get out of a room. Loki also let me know when I was going to have migrane headaches (which was a bonus because mine come on suddenly). Loki could open doors, call 911, he was my security system, and he could read people like I have never seen.
One of the coolest things I ever saw him do was when we were getting on the bus one day. The usual routine on the bus was that he would wait for me while I was paying and then go crawl under a seat. But this one day we got on the bus and he immediatly went up to this guy who was sitting in the first seat. He started sniffing and gently pawing at his knee. Then he started to whine and cry. I apologised all over the place, he had never acted like that before and as a service dog was not supposed to act like that.
A couple of weeks later we got on the same bus and there was the same guy. He said that after Loki went crazy on his knee he had gone to the doctor (had been having problems but thought it was nothing). Doctor said he had cancer. He said that he would not have gone to the doctor except for Loki. But because of him it was caught early enough that he was probably not going to lose his leg.
Anyway, now I have Jerron. She is a Border Collie/Lab Mix. Very smart. I am considering training her as a service dog but have not made up my mind on that one yet.