What does Genesis 9:26 mean?

In the previous verse, Noah cursed Canaan, Ham's son, as a result of Ham's extraordinary dishonor of his father (Genesis 9:24-25). The curse applied to their descendants, as well. Now, apparently to emphasize the curse, Noah blesses Ham's brothers. Here, actually, Noah blesses the Lord, "the God of Shem." Since Shem's line is the one that leads to Abraham and the Israelites, this may very well be the first hint that God will make Shem's people His people. This not only makes Shem the ancestor of the nation of Israel, it means Shem's ancestral line will produce the promised Messiah, Jesus Christ (Luke 3:36).

The curse on Canaan is repeated once more. Much later in history, the people occupying the promised land, the people Israel would conquer, will be known as the Canaanites. Many times throughout Israel's history, the Canaanites would be in conflict with and serve the Israelites (descendants of Shem). More pertinent to this curse, they would always eventually find themselves on the "losing side" of their conflicts with Israel.