The Group Health Seattle to Portland Bicycle Classic is the largest multi-day ride in the Northwest; 2013 marking the 34th annual ride.  My first time riding this event was 2012, making it a two day event with a friend, not too worried about timing - just being happy to be a part of it.  It's overwhelming to begin with as there are 10,000 riders that start off in 10 minute waves, if you haven't been on an organized ride, now is your time to start testing the waters!