This is a list of websites that I have found to have useful information on hikes in the area.
Washington Trails Association An organization of hikers that maintains a fairly complete list of trails, with trip reports.
TrailGuru Collection of GPS tracks, with few trip notes.
HikingNorthwest A large collection of trip reports and photos.
Mt Baker Snoqualmie National Forest Official government website for the National Forest.
Forest Service Trail Status — The latest information on trail conditions.
Forest Service Map — Mt Si