Mosaic Beach Studio, in Toronto, is a good place to start. Owner, Tanya MacFarlane is a self taught mosaicist and Mosaic Beach's full-time instructor. On March 1st Tanya opened a new studio - a working studio with classes and some retail hours (right now it's "by appointment" or "by chance" - of which she's very accommodating). It's located at 6 Carlaw Avenue, unit 201, and is a great complement to her long time running and easy to use online store.
If you're a newbie to mosaicing or a seasoned pro you'll find just about everything you'll need at Mosaic Beach Studio. Tanya knows her stuff and her passion for mosaicing is palpable!