Welcome Roman! Always nice to have another rider around. (and another poster in the biggest Canada section

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LBS - there's NO shortage of these in the GTA (Greater Toronto Area). Some areas more-so than other's, but tons, nonetheless. What you'll find usefull or not is, of course, up to you.
http://forums.mtbr.com/showthread.php?t=88133 (HAHA! ANOTHER Sticky!!!!!

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Same can be said for trails. Subjective, by far, as to what's good or not - as you've already noticed. Most of the "good" stuff is, IMHO, more accessible by driving for an hour or less from Toronto. There's at least a dozen places that come to mind.
http://www.theride.ca/ You can also check Trail Reviews at the top of every MTBR page.
As with others - might be a good idea to post your general location so other's in your area can better help you.
Mailorder ~> Canada - Ramsay's is a name that quickly somes to mind, as well as MEC (Mountain Equipment Co-Op). Ramsay's is based out on the East Coast (more or less) while MEC, although having limited supplies, is right in downtown Toronto. There are a few others, but the deals some from the U.S. mail order houses. We all know how this works.
Mailorder ~> US - you'll never get charged any duty on new or used bike parts shipped up from the U.S. You WILL get charged with taxes, however. 7% GST (Goods and Services Tax) and 8% PST (Provincialy Sales Tax) will be charged on anything you have sent up. Whenever possible have your stuff sent up using USPS - it's the cheapest, as per the business agreements made with USPS and CanadaPost. IIRC, you'll be charged a $5 flat rate (don't quote me on this). NEVER EVER have anything sent up using UPS or FedEx!!!! You WILL get hammered with Brokerage fees.
Basically, if you have something sent up from the U.S. with USPS take the U.S. dollar value, multiply by 1.55 and that's what you'll be paying in Canadian dollars (pretty close average with experience to back it up).
If you have something sent up with UPS or FedEx then do the same, but multiply by 2 instead of 1.55.
So, there you have it. Enjoy and hope to see you out on the trails!