Transportation Connections (www.transconnect.org ) is a private, nonprofit agency whose excellent website contains links to a wide range of public transportation companies in Washington. In addition to buses, they include car sharing, cycling organizations, Amtrak, and the state ferries.
Greyhound (206/628-5526 or 800/231-2222, www.greyhound.com ) serves most major cities in Washington, providing nationwide connections. Its main routes are along I-5 from Canada to Oregon, along I-90 from Seattle  to Spokane , and I-82 from Ellensburg  to Pendleton, Oregon.
Washington’s public buses offer a comprehensive system, with low-priced service throughout all of western Washington. The coverage is less complete east of the Cascades, but still good. Many buses have bike racks. On the Web, visit www.wsdot.wa.gov/transit  for a complete listing of buses, trains, and other travel options.
A number of companies offer multi-day motor coach tours throughout the Pacific Northwest. Two of the largest are Gray Line of Seattle (206/626-5208 or 800/426-7532, www.graylineofseattle.com ) and Tauck World Discovery (800/788-7885, www.tauck.com ).