The Jolly Roger Taproom is located at the north end of the Ballard bridge. It's worth going out of your way to try the mini burgers, or Lil Jollys as they call them. For a little more than $3 you get three miniature burgers along with a choice of several tasty dipping sauces. If you go for the version with cheese and grilled onions they are about $5. I would almost go so far as to say they are the best burger in Seattle.
The Jolly Roger also has fantastic onion rings and good beer.