If you visit the San Francisco Bay Area, the Monterey Bay Aquarium is a side-trip (about 2 hours south) that is worth taking.  If you can't make it there, however—or often enough, as is the case for me and my family—the Monterey Bay Aquarium's "E-quarium" web page is another great way to enjoy it.  The main page links to live web cams of their main exhibits, with additional links to various podcasts and their video library.  The page also features a link to "interactives" for kids, most being appropriate for preschool and elementary school kids.