Essential websites to view are: www.nps.gov for information on all national parks.
www.homeofyosemite.com has tourist information on Yosemite and Mariposa; they have invaluable, suggested itineraries outlined depending on which time of the year you visit and how long you've got.
Visit www.yosemiteresorts.us if you want to stay in hotel accommodation within the park.
www.calacademy.org has details of the California Academy of Sciences.
Other sites to visit include:
www.virginholidays.com (to book fly-drive packages and holidays to California)
www.holidayautos.co.uk for car hire
Yosemite Miner's Inn, www.yosemiteminersinn.com
San Francisco, www.onlyinsanfrancisco.com
Sunday Indo Living