I do some really intense skiing pretty much every weekend. And by intense, I mean the type of skiing that works your leg muscles really hard; powder skiing, mogul skiing, and the occasional jump (they actually do, believe it or not) as well as the occasional ski race (skiing in a crouched position is really hard on your legs, but actually strengthens them immensely).
Other than that, I also do a lot of walking (seriously, I walk like everywhere), and sometimes running as well. Mountain biking is another good leg strengthening exercise and I do a fair amount of that in the summertime.
For strengthening my arms, I also occasionally do some lifting, though I haven't really done much of that in some time. I've found my arms getting stronger everyday though, because of my line of work; I work at a furniture store, so we're always carrying heavy stuff upstairs and hauling 700lb fridges up and down stairs on dollies.
Then there's the fact that I'm a drummer, and when I do my almost daily drumming sessions, I go all out. I work on speed, accuracy, intensity. All of these things are great arm and leg exercises. And since I tend to play fast and aggressively, my arms and legs are almost always sore after a good 2 hour session.
And then there's all the snow shoveling I do. I tends to snow upwards of 3-4ft overnight, and then rain during the day, and the snow absorbs all the water, which causes the snow to become extremely heavy (150lbs per cubic foot at the worst). Spend 2-3 hours shoveling all that **** away, and you get some fantastic exercise out of it.
Even though I hate winter, it makes me stronger, lol.