These were taken a while back, but I've always enjoyed shooting at agility trials... especially when there were the Bouvier breed is running. One of our litters produced a Bouvier that was ranked #2 in the country for several years and even at 10 years old she was blowing away Boarder Collies in the ring.
Here are a few shots I got a various shows of other dogs...
They don't have as many agility trails in the Northwest as they use to and when they do a lot of them are inside barns or arenas. Since you can't use flash (even when they allow it you still shouldn't use it) it's more difficult to get good shots. Even when out doors is seems the agility committee never considers photography when they set up their rings. Ether all the good action obstacles are on the other side of the ring behind everything, you are shooting into the sun most of the day, the background is the worst it could possibly be, the direction they run is away from you rather than towards you, or all the above.
It's still a lot of fun.