Seattle, WA + Add a trip

The Seattle Central Public Library on 1000 4th Avenue. It's downtown; in a great building; has plenty of seating; I believe the wireless is free and open to all; and naturally, because it's in Seattle, there's a ton of coffee shops nearby, including one in the library. If you don't have a wireless computer there are also terminals available, but I believe there are restrictions on the usage of these.

More info: http://www.spl.org/default.asp?pageID=branch_central_computers&branchID=1

There are TONNNSS of places for free wifi... so many fun coffee shops all over town.

Check out this guide to search by neighborhood and see reviews:

seattle.wifimug.org

Along with almost every coffee shop (except Starbucks), there are a lot of free wi-fi bars as well that are cool places to hang out during the day. Including Fado on 1st and Columbia and Black Bottle on 1st and Vine.

Most all of the cafes in the U-district

Not just the central Seattle library, but all of the Seattle Public Library branches. Also, any Apple Store in the country has free wifi, and you can usually plop down out front without bothering anybody.