- Facebook : http://developers.facebook.com/
- Twitter : http://dev.twitter.com/
- Youtube : http://www.youtube.com/dev
- Google : https://developers.google.com
- Apple : https://developer.apple.com/
- Android : http://developer.android.com/index.html
- Sony : http://developer.sonymobile.com/wp/
- Mozilla : https://developer.mozilla.org/
- Joomla : http://developer.joomla.org/
- BlackBerry: https://developer.blackberry.com/
- Yahoo : http://developer.yahoo.com/
- PayPal : https://developer.paypal.com/
- LinkedIn : http://developer.linkedin.com/
- Ubuntu : http://developer.ubuntu.com/
I may forget some important sites or platforms but if I remember later on I can add them here again later on...