I just finished spending the summer in Chicoutimi, and it was incredible. If you do the Saguenay region, definately go to Tadoussac as well.
Tadoussac is where the St. Laurence and Saugenay rivers meet. It is absolutely incredible to be on a boat looking up at the massive cliffs that make up the fjord. It's really unbelievable. It is in fact the only true fjord in North America if I'm not mistaken. You can rent a kayak and tour on your own, or book a whale-watching tour. When I went we saw about 10 whales, including some belugas....There are also some very cool sand dunes in Tadoussac....beaches as well....
I didn't visit lac-st-jean as much as I would have liked. Some things that I wish I had done are: take the bike route around the le lac, visit the caves (I forget the name), visit the gardens. It is really amazing the amount of things there are to do around lac-st-jean....There are probably like 50 small picturesque towns surrounding the le lac that each have their own special attractions....example (St. Felicien - Zoo Sauvage, Val Jalbert - Ghost Town - Coolest Waterfall EVER - Old Rusty Mossy Very Cool Mill.....etc)
I would highly recommend calling tourism Quebec and requesting a pamphlet for the lac-st-jean saguenay tourism region....
Oh yeah, another thing to do...which I didn't get to do....is to go on these very cool sort of "in the trees" obstacle course parks. They are basicaly obstacle courses that are like a hundred feet up in the air, built in a forest....they also have cabins built in trees where you can rent a room over night and stuff....They are all over Quebec, but there is one that is like 15 minutes from Chicoutimi, and another one somewhere in lac-st-jean area I think.....
Another area to visit is the Charlevois (not sure on spelling) tourist region. It is basically another route you can take from Quebec City to Sagaueny, where you drive along the St. Laurence north to Tadoussac. Tadoussac is actually part of three regions ( lac-st-jean saguenay, charlevoix and another one)....I haven't been there but I think it would be a cool place to go....and a nice drive....
Also - The drive north from Quebec City to Chicoutimi is AMAZING! For an Ontario who had never before driven through mountains it was really breathtaking. There are numerous National Parks along the way where I think you can camp....really incredible scenery. And also kind of funny when you see about 4 different alert levels for moose crossings.....I saw one moose run across a highway....
ALso - in Chicoutimi there is a festival called Rythmes du Monde at the start of August that is pretty cool....they close down the main street and basically turn it into a huge party ground for a week...During the day its cool for families with face painting....music...dancing...performers...etc...and at night the music takes it up a notch, you can drink in the street....all the bars/restaurants build temporary extension to their patios...its awesome....
Also - In Roberval (one of the larger towns around lac-st-jean) there is some good stuff to do. They have some sort of festival of foods or something that I dont really know about...in July I think...And in July or August (I forget) There is this thing called La Traverse....where there are a bunch of swimming events...The big finish is an event where people swim across one part of the lake (32 km...its like an 11 hour swim....)
http://www.traversee.qc.ca/en.php
The yearly event is somehow connected with FINA....
Also - (Sorry this is so long) The bike route around lac-st-jean...It is I think around 250 km. You can rent/bring a bike and everyday just bike as far as you want and then camp or stay in a bed and breakfast or whatever and then bike further the next day. I think its the best way to tour all the towns around lac-st-jean...and you can take as much or little time as you want...Theres also a bus service that will transport your luggage from stop to stop so you dont have to carry it with you on your bike....really cool idea....
Anyway, thats it for now. Good luck and I would highly recommend calling 1-800-BONJOUR and having them send you the tourist guides for whatever region you want to visit....
One more thing.....On the drive from Quebec to Chicout....Fill your gas tank every chance you get, because there are very few gas stations between and you do not want to get stranded in the mountains....