Google Capture the Flag 2017 - Google's 2nd annual worldwide security competition
WrapAPI - Build an API on top of any website
Startup Security Program by Templarbit - Security practices & tools required to close large deals
Airtable - Airtable works like a spreadsheet but gives you the power of a database to organize anything. Sign up for free.
The Security Checklist - The Practical Security Checklist for Web Developers
Albato - No matter the process. Automate it with no-code.