HandUp Gift Cards - Give directly to a homeless neighbor on the street
Y Combinator Companies - Interactive list of all 1000+ YC companies
Catchafire - Use your professional skills to help charities
Apply to YC (Y Combinator) - Curated collection of resources for founders applying to YC.
TAP London - Tackling the homeless problem together
Startup School - How to start a startup, by Y Combinator