Sit in the world's first Starbucks
In 1971 Starbucks was founded in Seattle. Even if you're a hater of their famous coffee, to sit in the original shop on Pike Place and drink in a little of the history of how it got its name and grew to 18,000 stores worldwide, is cool. There are usually long queues (but just around the corner is the Seattle Coffee Company).
Take an Underground Tour of the city
In 1889 the Great Fire of Seattle burned down 25 blocks of shops and businesses built on low-lying flood plains on the waterfront. Consequently it was decided to rebuild one storey higher and lift the city up from the water. But no one could wait ten years for that to happen so owners rebuilt on their original sites while the new street level was created. Today you can wander through underground streets and derelict bars and hear hilarious tales of life and skullduggery back in the day.
See Megan's photo tour of the abandoned buildings here.
Go to a ball game
Who doesn't like the razzamatazz of an American ball game? In Seattle you have two stadiums side by side. If it's baseball season, tickets to the Seattle Mariners are about $12 at Safeco Field and you can pretty much just walk up. But football is another matter. The Seattle Seahawks play at CenturyLink Field and tickets for the season go on sale in late July or early August. Games are usually sold out. You might be able to pick one up through the NFL Ticket Exchange.