I am fascinated by Canada's many (and I do mean many) territorial disputes. The most significant of these are the Arctic waters. Canada claims them all as internal waters; it is the only nation in the world that considers Canada to have a claim to them at all -- everyone else, including the United States, considers them international waters. The United States has on multiple occasions, with great deliberateness and noise, sent its ships through the waters without asking permission. Canada, while continually insisting that it owns the waters, has tended to turn a blind eye to this, precisely because it has had neither the resources nor the clout to face the U.S. down on this point. However, Stephen Harper, the new Prime Minister of Canada, has made a special point of saying that he will build up Canadian presence in the waters in order to protect Canada's claim to them.
The Arctic waters will become more and more significant due to melting ice. As the Arctic ice has melted, the waters have become more navigable; if it continues to do so, the Northwest Passage will finally open up as a feasible route for shipping (currently the passage is only navigable briefly during the summer). Canada has an interest in making sure that it will be a Canadian passage; everyone else has an interest in making sure that it will be an international passage. It will be interesting to see whether the dispute ever reaches the level of a direct confrontation. At present Canada doesn't have the means to press the issue much; but Canadians, docile and complacent as they may often seem, can become rather bold and fierce when roused.