Monterey Bay Aquarium
886 Cannery Row, (831) 648-4800
Open daily 10am-6pm.
Admission approx. $12 for adults, $6 for kids.
Advance tickets (to prevent standing in line) can be reserved by calling (800) 756-3737 (although they have a $3 service charge for this).

Also see their website at http://www.mbayaq.org