Deep Zoom is a very cool mash-up using Bing Maps and the NOAA nautical charts. By tapping into the NOAA database of tide and current tables, you can see right away what’s going on in your area. The author of the program has made it very clear that it’s strictly a reference tool and not for navigation so don’t use it when pulling into the harbour with your ocean liner.
If you are wondering what the giant arrow is in the middle of the capture, it’s for Deception Pass in Washington State which was maxing out at 7 knots (14km/h).
(Turn the sound down and jump ahead to the 5 min mark. It gets a lot more interesting there.)
The site does require Silverlight to be installed on your computer so it might not work on all work computers (especially if you have a very conservative IT department like my work...).