chachalaca posted another weblink today that led me to this very informative and helpful article.

It's been several years since I took the Victoria Clipper between Seattle and Victoria, but I recently rode on the Washington state ferry between Bainbridge Island and Seattle (along with our rental car). I was impressed at its timeliness and ease of use. Not to mention the views of the beautiful skyline!

Seattle Times - The Many Ways to Travel between three cities

That's a good, comprehensive article. Vancouver Entertainment Books have a 50% off coupon for the QuickShuttle, which is often useful. There's also sometimes a $49 roundtrip rate, which I think applies to weekend trips.