I've been to A-1 in Toronto and they have quite a lot of stuff, but it's mostly in piles everywhere. It's the Sanford & Son of electronics surplus. There's just stuff everywhere that you have to sift through, but you can find some good items. They do have some stuff organized like pots, knobs jacks, LEDs, switches etc. Their website has a lot of info, although there's no guarantee about stock.
They have a big selection of pots in various values, tapers and multi-gang configurations (no Alpha or CTS though). They have DPDT switches, but they are expensive and look like Taiwan X-Wing. I didn't see any 3PDT switches. They've got lots of Hammond enclosures.
I'd say their prices are average for the most part and a little on the high side for some items. I'll definitely go back to sift again.
Sayal has a lot of items, but you'll pay for the convenience. They are one of the only locals to have metal film resistors.
Honson Computer on College just West of Spadina (inside Home Hardware) has a very organized selection of resistors, capacitors, transistors, IC's, diodes, pots and some other items. No enclosures that I saw. Good prices on components and 1% Carbon film resistors.
I still can't find any local sources for Alpha & CTS pots, switchcraft jacks, good DC jacks & 3PDT switches. It still comes down to ordering from multiple sources to find all the stuff you need.
As for ordering online, I'm new to DIY effects and I've only ordered once from Pedal Parts Plus. Shipping seems to be $19 US to Canada regardless of what you get.
Tubedepot.com has Alpha & CTS pots at decent (but not the best) prices. They also have Carling DPDT switches for $8.95. Not to mention a lot of boutique components and I got a shipping quote of $6.95 US, so I'll probably place an order to try them out.