If you have visited the Niagara wine region before, I'm sure that you have come to possess one or more copies of the official wine route map and brochure. I find that I never can find the map when I'm planning a trip so instead of tearing the house (or car) apart looking for it, I found the PDF versions of both the map and the official winery brochure on the Wines of Ontario website.
PDFs of the driving map and the official 2008 guide to wineries (low res or high res) can be found here.
The map is quite up-to-date, although a couple of special places like Hidden Bench remain, well, a little hidden. If a new up-and-comer isn't on the official guide yet, let Google Maps locate them for you.