There's a neat article in today's Seattle Times about beachcoming for glass.
It mentions a favorite in the Port Townsend area. The Port Townsend Glass Beach. Again, since its well known to the public, they mention that it is an area that will probably be picked clean by midsummer.
A fun read for people that like to look for rocks and other fun things when at the beach.
Some people have even made a business out of it, making sea glass bracelets and rings.
For more information, there is a book "Pure Sea Glass", written by Richard LaMotte.
There is also the North American Sea Glass Association http://seaglassassociation.org/