Before you take a river cruise on the Mississippi, you must read "Life on the Mississippi" by Mark Twain. He was a pilot on steamboats on the river just before the Civil War. It's great of course and it covers so many interesting aspects of the river that you would never know about unless you read it. I highly recommend it.
Also if you want to learn more about river cruises and cruises in general I found the site "Vacations to Go" to be really helpful. Here's their River Cruises page:
http://vacationstogo.com/river_cruises.cfm
Their reason for being is to offer last minute deals on cruises, but you can read all about the different cruises available, where they go, their duration, the companies that run them, and about the ships. I think you might have to register to read the site (to see prices), but it's free. I thought the river cruises sounded really appealing and also the New England cruises too, my mom did one that left from Boston and went up into the Maritime Provinces - how cool.
Where I live out here it would be so easy to get on a cruise to Alaska, I could hop on the Cascades, get off in Vancouver BC, take the SkyTrain right to the cruise terminal - just a hop skip and a jump for me and I'd be on my way.
Or, even easier, if I wanted to take the Alaska Ferry, I could take a 75 cent bus ride to the ferry terminal and I'd as good as be in Alaska already.
