The Stiller Foundation (FB link) is a real charity, founded "to support children around the world by providing educational opportunities to help them realize their full potential."
The PSA, however, is just good old fashioned Stiller humour:
The URL is the best part, considering Aniston is one of the more modest and guarded blockbuster actresses out there. (Don't worry/get too excited, it just redirects to FB.)
Via Illegal Advertising