There are lots of articles on the web now about paddling the inside turn. Depending on your boat and how it is loaded you can get the canoe to turn, and continue to turn toward your paddling side. If you make the turn wide (large) enough it will be a straight line.
In larger canoes (e.g. 16 feet+) move your weight back and heel the canoe. At some point the canoe will turn to your paddling side because of the underwater hull shape. Adjust the heel until you can paddle straight against this tendency to turn - no more 'J' stroke.
When sitting closer to midship or in small (solo) boats a bow wave can be set against the stem of the canoe by heeling the canoe and initiating an inside turn. This 'wave' will hold the canoe and carve an inside corner - similar to the above turn you can paddle against this tendency without having to do any correction strokes. Periodically you may need to do a cross forward stroke (or two) to reset the bow wave.
The thread on paddling.net for some discussion http://www.paddling.net/message/showThread.html?fid=advice&tid=1300284#1300460