There are many places to search for jobs and internships online. Here are some places to start.
April 2020 Update
Here is a great list compiled by Candor on companies that are still hiring, or have hiring freezes and layoffs: https://candor.co/hiring-freezes/
Job search sites
Biospace.com (Life sciences jobs): www.biospace.com
Cal Apprenticeships: http://www.calapprenticeship.org/
Cal Jobs: https://www.caljobs.ca.gov/vosnet/Default.aspx
CareerBuilder.com: www.careerbuilder.com
DICE.com (Tech and IT jobs): www.dice.com
Eco Jobs: http://www.ecojobs.com/natural-resource-and-conservation-jobs.htm
Employer Search Tool: http://www.labormarketinfo.edd.ca.gov/aspdotnet/databrowsing/empMain.aspx?menuChoice=emp
Glassdoor: https://www.glassdoor.com/Students/index.htm
Government Jobs: https://www.governmentjobs.com/
Higher Education Jobs: https://www.higheredjobs.com
Idealist.org (opportunities at nonprofit organizations): www.idealist.org
Indeed.com: www.indeed.com
K-12 Education Jobs: https://www.edjoin.org/
LinkedIn Jobs: https://www.linkedin.com/jobs/
Local Jobs: https://www.localwise.com/jobs?locs=san-jose-ca
Monster.com: www.monster.com
Resume Builder: https://www.resume-now.com/
Simplyhired.com: www.simplyhired.com
TransitionsAbroad.com: www.transitionsabroad.com
USAJobs.gov (federal government jobs): www.usajobs.gov
Internship and Volunteer Listings
Internships.com:https://www.internships.com/
Intern Abroad: https://www.goabroad.com/intern-abroad
WayUp internship listings: https://www.wayup.com/s/internships/
UC Berkeley careers site: http://career.berkeley.edu/Internships/IntCurrent
VolunteerMatch.org: www.volunteermatch.org
Networking sites
Guide to following up with employers: https://www.wayup.com/guide/the-ultimate-guide-to-following-up/
LinkedIn Alumni Tool: https://university.linkedin.com/content/dam/university/global/en_US/site/pdf/alumni-tool-final.pdf
Tips for reaching out to someone you admire on LinkedIn: https://www.themuse.com/advice/4-tips-for-reaching-out-to-someone-you-admire-on-linkedin