Facebook - https://www.facebook.com/security/2fac/setup/intro
Twitter - https://twitter.com/settings/account/login_verification
Slack - https://silgtis.slack.com/account/settings/2fa_choose
Instagram - https://www.instagram.com/accounts/two_factor_authentication/
Dropbox - https://help.dropbox.com/teams-admins/team-member/enable-two-step-verification
Have more suggestions? Contact 2sv@sil.org!