If you want something that isn't very popular, do Mount Buller. It's in K-Country, and I've only been there once, but I've heard that very few people ever climb it. It's definitely a workout, though. Mt. Rae is also a workout, since you start above the treeline, and it's still a complete climb. Not a lot of air up there.
Sparrowhawk is great, as is Yamnuska. If you haven't done Indefatiguable, you have to. Don't do it in August, though, because that's buffalo berry season, and a mother grizzly likes to hang around Indy, forcing the rangers to close the trail down.
For a nice 4 day trip, there's a really cool loop you can do that involves Three Aisle Lake. It's not very difficult for the most part, but it's a fantastic adventure, if you've got 4 days. There's something about camping only with stuff that you can carry on your back that appeals to me. The beer gets heavy after a while, though. I did this trip 10 years ago, and can't remember if the trail has a name, but I do remember that it was a blast.
Pick up the Rockies scramble guide that flamingchina was talking about. Very good book, and gives you all the information you should need before you set out on your hike.
Ribbon Falls is a nice one as well if you're taking the wife or gf.
It is my goal in life to climb Kilimanjaro before I'm 40 years old. It's a bit of a drive to get there, though. Highest scramble in the world.
Hey, if you want to see a few different scrambles and some trip reports, visit my buddy's website. He's an avid outdoors guy.
www.fresho2.com
Lots of good stuff in there. The site doesn't look good with Firefox. Open it with IE.