In addition to the building permit database, Seattle.gov provides a dataset for historic buildings at:
https://data.seattle.gov/browse?tags=historic+register
Any building in Seattle that is a public housing or multi-family housing inspected for public housing assistance program will have info in this HUD dataset:
http://www.huduser.org/portal/datasets/pis.html
The footprints and building heights are commercially available ($1571) at:
http://market.weogeo.com/datasets/nokia-here-buildings-seattle-wa-metro-region.html
Other than that, the best way to get this information free (or near FREE) is to go to the property tax office for King County and see if they provide a electronic copy (e.g., like on a CD) for a fee.
UPDATE: I found some more links on building lot outline in major cities open data. This comes from stackexchange question: https://gis.stackexchange.com/questions/2046/where-can-i-find-building-footprint-data/2050#2050
Chicago: http://data.cityofchicago.org/Government/Boundaries-Buildings/w2v3-isjw
Seattle: http://data.seattle.gov/dataset/2009-Building-Outlines/y7u8-vad7
Bellingham: http://www.cob.org/services/maps/gis/index.aspx
Bloomington: http://bloomington.in.gov/documents/viewDocument.php?document_id=1870
Spokane: http://www.spokanecity.org/services/gis/data/
Kitsap County: http://www.kitsapgov.com/gis/metadata/
There is also some additional data for several cities across the U.S. and federal data on building permits from Data.gov.