For marathon races check the following links:

New York Marathon Canoe Racing Association (New York State)
St. Lawrence Valley Paddlers (Northern New York State)
Mac's Canoe Livery (Northern New York State)
New England Canoe Racing Association (New England)
Ontario Marathon Canoe Racing Association (OMCRA)
United States Canoe Association
Canoe Kayak Canada

For North America's top sprint events:

Canoe Kayak Canada
USA Canoe Kayak
Lake Placid International Regatta