Here's a good article on CNN about how to visit Alaska without taking a cruise.
If your going to drive through Canada, make sure you bring your passport. Alaska is the only state that you have to drive through a foreign country to get to it. Since 9/11, a passport is required and makes it a lot easier. You will be going through both U.S. and Canadian Customs.
You'll also have to have a major credit card or $500 for an emergency. On the Alaskan Highway, services can be spread out a bit. It's a serious trip, so be prepaired. But, it's a trip you won't forget.