Ice wineries are primarily located in Niagara. It is a great day trip-only about 11/2 hours from TO. Most wineries have tours and some have exquisite restaurants.

There is LOTS of variety, including a less sweet Cabernet version.
I like Kittling Ridge Icewine & Brandy. It's available at most Ontario liquor stores for around $22.

http://www.kittlingridge.com/products.htm

Warning is smart but QUALITY ice wines are not in the outrageously sweet category. Germany and Austria (the two other places besides Canada where you can find true quality ice wines) are the original producers of icewine but Canda is the largest producer. I also believe there is a winery in OR, USA. Riedel wine glass company has ice wine glasses which really do enhance the flavor (in our opinion AND they were developed with the input of Canadian ice wine specialists).

Sometimes trtyin new things isn't fun. I suggest you buy a small "airplane" bottle first. Icewine is quite sweet and not for everyone.

Ice wine is at any liquor store (LCBO) in Toronto, but as it is rather expensive. I suggest buying it at the airport when your are leaving.

The Niagara wine region is filled with wineries that offer tours and is very close to Toronto (about a 90 minute drive). Popular wineries are Iniskillin, Vineland Estates, Hillebrand and Cave Spring.
For more info:
http://winesofontario.org/

There are some wineries that produce ice wines in Niagara-on-the-Lake. Niagara-on-the-Lake is located about 90 minutes south of Toronto right off of the QEW (maybe the 2nd or 3rd exit before the US-Canadian border?) I think that there are winery tours that you can take from Toronto to Niagara-on-the-Lake that are daytrips or you could stay in Niagara-on-the-Lake for a day or two and arrange to take a tour of the wineries through your hotel. I drove over to Niagara-on-the-Lake when I visited Niagara Falls in 2005 and I really liked it. The town center is very nice with a lot of old buildings, restaurants and boutique-type stores.