I know that a lot of people have given you a great deal of advice, but I think a breed from the sporting group might be a good choice. They are breed to hunt all day (not every day, but you know), they love to play and hike. I have a German Shorthaired Pointer, and they are active. You can take them out hiking, biking, running, etc. and they LOVE it. They are also very versatile. They can play all day, and curl up on the floor (or your lap ). They love to cuddle and get kissies. They are obedient, and VERY intelligent, probably not as intelligent as a Border, but they are pretty smart. I think I have a more mellow GSP, according to people who have owned GSPs. She's got enough energy for me though! Heres a good website to read up on them:

German Shorthaired Pointer

Heres a German Shorthaired Pointer Rescue:

GSP rescue