Goldens have an excellent reputation for agility. They are active and VERY trainable. Also, I'd check out some AKC working dog shows for other breeds that might be of interest to you, and also Dog Fancy magazine. It can be a great resource.
labs, border collies and australian shepherds seem to be great at this sport. I love to go to the shows and watch them. It's amazing what they can do. My boss has her lab in a show this week up in Maryland. This is her first real competition. She is smart as a whip and loves to perform.
I just lost my Shetland Sheepdog in December. I love the breed and know they also make good agility dogs. He was absolutely the smartest dog I had ever seen. It was like he knew the English language. He was so perceptive to everything around him.
I have a pembroke welsh corgis and heve just started agility training at the local dog obedience school. It is going very well.!! She is so smart and she loves it. She is pretty fast for a dog with short legs!!
i know your not looking for this type of dog but i've done agility work with my pit bulls and they are great with this sport!!! but if i had to choose between a border collie or aus. sheperd it would have to be a aus. sheperd.mainly because i like the red and blue merals. have fun with this sport its great exercise for both you and your dog.