Vancouver Island is a large island off the coast of British Columbia, not far from Vancouver city. Most travellers will be arriving there from Vancouver or its environs (although it's also possible to travel to the island from the US). This article covers the options for travelling to Vancouver Island from mainland Canada.
The island is 270 miles long (stretching roughly along the NW-SE axis) and approximately 70 miles wide, although the spine of the island is mountainous while the coast often indented and thus the actual road distances are much larger.
The principal way of travelling to Vancouver Island is by using the services of BC Ferries. Vancouver has two ferry terminals, one south of the city in the suburb of Tsawwassen (technically in Delta) and another in the north west (technically in Western Vancouver) at Horseshoe Bay.
Tsawwassen has frequent (hourly for most of the day) connections to Swartz Bay, 20 miles from the island's (and BC's) capital Victoria. There are also several daily ferries to Nanaimo, located 80 miles up from Victoria along the eastern coast of the island and the best launching pad for the west coast resorts of Tofino and Ucluelet. The crossing to Victoria takes 1h 40 minutes, and to Nanaimo 2 to hours. Horseshoe Bay has several ferries to Nanaimo, usually every two hours during the day.
There is also a connection from Comox (about half way up the eastern coast of the island) to Powell River on the Sunshine Coast.
At the time of writing (2010), the crossing costs 14 CAD per passenger, and 47 CAD per car (children aged 5 to 11 are half price and under fives travel for free), Powell River to Comox is slightly cheaper.
The precise schedules and fares can be checked on the BC Ferries site at http://www.bcferries.com/schedules/mainland/
The choice of the route thus depends entirely on the destination on the island and their initial location in Vancouver. If you are travelling to or from Nanaimo without the car, the journey from the Horseshoe Bay downtown is easier (one express bus) than from Tsawwassen (bus and SkyTrain, or possibly two SkyTrains).
If you are planning to tour the island (or, as it's often the case, its most popular parts, i.e. Victoria and the west coast resorts near Pacific Rim National Park) then the best option is to take a ferry to Victoria from Tsawwassen and then return from Nanaimo to either Tsawwassen or Horseshoe Bay. Both of these routes are very scenic and I personally think that it's nicer to arrive in Swartz Bay (you get a good look at many of the lovely Gulf Islands on the way) at one end and at Horseshoe Bay at the other end (the approach to the mainland is very beautiful here, with good views of the mountains).
Tour companies offer joint tickets from Vancouver to Victoria, but these costs about a double of what it costs to travel by public transport (approximately 45 CAD one way) and frankly are not worth the bother unless you have a lot of cumbersome luggage. The double decker city bus from Swartz Bay to Victoria takes you all the way to the centre of the city for all of 2.50 CAD and runs frequently.
You can also, of course fly to Vancouver Island, although it's by far the most expensive option, with the tickets costing at least around 100 CAD one way.
Island Express fly from Abbotsford to Nanaimo and Victoria, Air Canada has scheduled services to Victoria from Vancouver, Calgary and Toronto and from Vancouver to Nanaimo, Pacific Coastal Airlines fly to Campbell River, Comox, Port Hardy and Victoria to Vancouver while WestJet fly from Kelowna to Victoria and from Calgary and Edmonton to Comox.
The fastest and most exciting way to travel to Vancouver Island is by float plane, with several companies providing connections directly between downtown Vancouver and downtown Victoria as well as to Nanaimo. Campbell River and numerous other island communities. It's also likely to be the most expensive way to travel, with one-way tickets from Victoria to Vancouver around 150 CAD or more.