I found this excellent website the other day called marinas.com. It has an astounding amount of information on it, covering countries all around the world with access to marina directories, videos, charts, weather and more.
The marina data has been extensively integrated with Google Maps. You can quickly toggle map overlays like Marine Services, Bridges, Locks, Ferry Terminals, Anchorages, you name it. What’s really interesting in Google Maps is the nautical charts. If you zoom in close enough many area’s have chart data like this one of the Toronto harbour.
You can also view the charts in Google Earth which I have not tried yet. Google Earth is addictive enough as it is. In the huge marina database there are thousands of aerial photographs, you can really get lost on this site, highly recommended.