I have often found that flying to Amsterdam is the least expensive way to get to Europe, at least from Toronto. I have used major airlines, including Air Canada, and also the charters, like Martinair.
I have found deals to London, but then there is the expense and hassle of getting from England to the rest of Europe. I once bought a ticket from a travel agent that included a one-way train ticket from London to Paris via the chunnel!
But normally, I find Amsterdam the best jump-off for European tours. For reasons I do not fully understand, travelling from Holland to other destinations in continental Europe is trivially easy. Hop on an overnight train and you are there! (And of course, Holland is a lekker biking destination in its own right.)
A couple of years ago I lucked into a surprisingly cheap flight from Toronto to Zurich! On the way back, I had to fly home from Milan with a stopover in Frankfurt, but it was a small price to pay.... especially since I was cycling from Zurich to Milan! So if it's Switzerland you want to get to, keep your eyes peeled for specials.