Len's mills has one of the more atrocious websites I've ever had the displeasure of visiting, but their quality and price is about as close as you're going to get to Jo-Ann's in Canada (In fact if you check out the selvedge on the fabric, you'll see quite often that it's actually the Jo-Ann's internal brand.) They also carry Moda and higher end brands, granted, you're back at the $17/yd price we're oh so very used to.
I second the opinion recommending Creative Sister's sewing in KW. Their Full Moon Frenzy is a fantastic sale, and well worth a trip into town for it. While you're in the area, also check out greenwood quiltery over in guelph, and there are a number of small, amish run stores right in st jacob's (The name escapes me, but there's one not far from Reichard's that looks like a regular house except a small sign - it's on the main drag.)
If you're more towards Niagara, the Quilting Bee in Fonthill just underwent a major expansion, and words cannot describe how helpful the women are there. If you're in Toronto, there's a lot fewer shops than you'd expect, but there's a good workshop downtown called, interestingly enough, "the workshop" - lots of modern fabrics and a cool atmosphere.
If you're in Toronto and you're into texture arts, check out G&S Dye.
What blogs do you like? That'll provide a big hint to me/us as far as where to recommend.
If all else fails, look into the Lewiston UPS store. I use them, and they're awesome. They offer one-time package acceptance of US packages for $10 a pop, and you can rent a box there for about $140 a year. Then you can walk it back across the border yourself.