IN/NEAR DOWNTOWN
Lace up the comfy walking shoes, because this city is going to look great on your FitBit. Or, let the downtown buses cart you up the hills, and then walk back down.
NORTH
Space Needle. Because... c'mon. It's Seattle. One trick: if you go for a meal in the rotating restaurant (not cheap, but certainly a great view), access to the viewing deck is included.
Duck tour - leaves from the base of the Space Needle, drives through Pioneer Square, the Waterfront, and then up past the floating homes (a la Sleepless in Seattle) and into the water near Gas Works Park for a float around Lake Union.
Experience Music Project/SciFi Museum - Seattle is nothing if not known for music. The EMP (that guitar-colored blob below the Space Needle) tours you through the history of Seattle grunge, and lets aspiring musicians play in the Sound Lab.
CENTRAL
Library - colorful, fun, free.
Benaroya Hall - visit the symphony, or just stop in the lobby to see the Chihuly art.
Pike Place Market - see the clock, the life-sized brass piggy bank, and the fish throwers at the corner of Pike St and Pike Pl. Head down Pike Place to peruse shops, get free samples from Beechers Handmade Cheese and pass the original Starbucks.
Westlake Center - outside is a fun brick patio and a fountain that kids play in during the summer months. This area also houses the huge Christmas tree and carousel during the holidays. In the summer, you can find live music and other events. Political rallies, parades, and all kinds of activity centers here. Inside is a pretty run-of-the-mill shopping mall, with an entrance to the underground bus tunnel (the closest Seattle gets to 'subway'), and a food court at the top.
Also at the top of Westlake Center is the Seattle Monorail, built for the 1962 World's Fair. Take it for an easy ride to Seattle Center.
Olympic Sculpture Park is an extension of the Seattle Art Museum. Free, outdoors, waterfront views. Great for an outdoor walk or picnic.
Waterfront - the piers offer casual fish-n-chips style dining, endless souvenir shopping, and other weird stuff like the Ye Olde Curiosity Shoppe. From here, you can easily hop a ferry ride to one of the islands.
SOUTH
Pioneer Square - the original Skid Row, site of Seattle's humble beginnings. Art galleries, the pergola, fire fighter statue, totem pole, and Elliott Bay Book Company.
Underground Tour - fun, scandalous story of Seattle's origins. The tour is kid-friendly, but packed with innuendo. I heard a rumor about a happy hour version that is a little more... um... revealing.
Smith Tower - the small white pointy building at the end of the skyline. The first Seattle skyscraper, this building has elevators that are still run by uniformed operators, and drop quickly enough to make your stomach lurch. Visit the balcony of the Chinese Room for views of Mt Rainier (well, if it's clear), Puget Sound, and the downtown skyline.
Like sports? Visit Safeco Field, with its retractable roof to keep baseball games. Or see the CenturyLink Field, where they don't care how wet the football players get. I'm still amused people refer to this area as 'SoDo'... short for South of the Dome... when the Kingdome was demolished in 2000.
International District - great dim sum. Other than that... you're on your own.
WITHIN A METRO BUS RIDE (IF YOU MUST)
Bus routes change... I'm not going to try to keep current. Check out the King County Metro site, and use the trip planner.
Agua Verde: rent a kayak for a paddle around Lake Union, and then sit back and drink margaritas.
Fremont: self-proclaimed center of the universe. Cool shops, architecture, statues (including the Fremont Troll). Get there early on for good seats at the Solstice Parade... keeping in mind that the not-so-official naked bicyclists always kick off the festivities before the official parade start.
Capitol Hill - great shopping and restaurants, drag queens and pride parades, and possibly the best coffee in the city (thanks to Caffe Vita)
SUCK IT UP AND RENT A CAR
Boeing Factory - see the newest Dreamliners going through production in the largest building on earth.
Mt St Helens - it's surreal. Photos don't do it justice. Drive all the way up to the Johnston Ridge Observatory on a clear day. Check the VolcanoCam before you head out to make sure the drive will be worthwhile.
Take the ferry over (or drive around, if you want) to the Olympic Peninsula. Visit Sequim's Lavender festival in mid-summer, and drive the windy road up to Hurricane Ridge for spectacular views on a clear day. Again, check the webcam for current conditions.
Ladies! Spend a day relaxing in Lynnwood at Olympus Spa (or as I like to call it, the "naked lady spa"). Don't worry... you get little cotton robes to wander around in, so the nudity is very tasteful. Even if you don't splurge on a massage, facial, or other services, you can still wander around and get lost in the earth energy rooms.
Woodinville Wine Tasting - About half an hour from Seattle, this small town hosts several big-name wineries, as well as a number of tasting rooms where you can enjoy Washington wines. Here's a map.