In my younger days I used to take a rec boat down the upper portions of the Winchester Wasteway where it is more like a class II creek until I almost killed myself in a obstructed culvert. My recommendation is to avoid rec boats.
If you are going to try your hand at tandem canoeing and OC1 I recommend getting a good mid sized tandem like a Vertige X, Caption, or a Nexus. If you and your partner are no more than about 150 each you can include boats in the 12-13' range in this category. Then you can outfit them with movable saddles to allow for tandem and solo paddling. See my photo album called Capable Caption for a better explanation.
If you want to OC2 only then stick to the midsized and small sized tandems (like the Octane92). The big 16' and bigger boats are a little too unwieldy for most of the runs around here. That being said, if you can find a decent Dagger Dimension jump on it.
In the OC1 category I would recommend looking at the edgier boats out there since you already have a kayaking background. The Viper, Ocoee, Quake, Spanish Fly, L'edge, Option, Ion, and there ilk will be boats you will get much more out of and will keep you interested longer. Stay away from the Maxim and the Prelude unless you want a really steep learning curve.
Once you get your gear in order you should be fine on any of the beginner kayak runs in the area. If you are class III kayakers then you probably won't need to spend as much time as you think in class I-II water to get a good feel for canoeing.
My biggest piece of advice to anyone who takes up the open canoe is to get a bombproof roll. For some reason rolling is seen as optional by many canoers. Many more learn to roll but never get a combat roll. If you have a roll you will find a lot more people who will boat with you on a wider variety of rivers. Even a OC2 can be rolled.
I have a Probe 12 solo, a L'edge, and a Caption that is set up as a tandem. If you want to boat sometime let me know and we can go hit something like the lower Sky, or the lower Chilliwack. I'll bring the boats.
In addition to the resources that have already been listed there is the Beaver Canoe Club in Canada, and the Lower Columbia Canoe Club in the Portland/Vancouver area. Paddlenet is a Vancouver based canoe version of PP. They organize trips, and hold pool sessions (albeit north of the border). Their website is
http://paddlenet.myfastforum.org/index.php.
Kyle