Shell Aerocentre @ Ottawa Macdonald-Cartier International Airport

This is a high-quality FBO (a bit nicer than the Esso Avitat next door), but also pricey, with lots of fees and expensive gas. If you're meeting customs, you have to make at least a short stop at the Esso or Shell (your choice), but otherwise, if you don't need the shiny FBO, the Ottawa Flying Club on the north field is a less expensive option for fuel and parking.