In case you’re not up on your acronyms, Sound Transit’s draft 2009 Service Implementation Plan is up on the web. There’s over 100 pages of stuff; some of it (as the name implies) is the service plan for next year and several years afterward. The big service changes in 2009 are the route modifications to the 554, 555, and 556. You may not have heard this, but there’s apparently some sort of train opening up next year as well.
The real meat, however, is extremely detailed ridership data for every route in the system. If you have a couple of hours to spare, it makes for pretty informative reading.