The best site I've found that discusses safety is https://www.boatsafe.com. Before you
do anything else, go there, bookmark the page and start reading.
Here's a good link that describes some safe sailing basics for all ages. Thanks to Brittney B. age 8, for the link!
Here's a great explanation of clouds and basic weather courtesy of NASA. If you need to check your weather, go to weather.gov.
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Learning important knots
AnimatedKnots.com
is a great website devoted to knots. You can watch them in slow
motion and see all the steps to most of the knots you'll likely use
aboard a boat.
Safety while sailing
Here's
an article about clothing that'll keep you safe.
Things to consider when sailing offshore and general seamanship.