UCSB and UC resources:

Tools for locating open access articles:

Google Scholar or Google
Search by article title to find open access versions of an article. In Google Scholar, look for an “All versions” link underneath the record.

Open Access Button
Find open access articles using the search function, or the browser extension (search by title, DOI, or PMID), and to request a free version from the author if not found online.

Unpaywall
Find open access versions of publications from over 50,000 publishers and repositories. Use the browser extension to auto-search article DOIs.

Miscellaneous resources

Sherpa Romeo aggregates and analyzes publishers' copyright and open access journal archiving policies.