Stripe and Mailgun and Twitter are some of the best documented, clearest to use APIs. The Google Maps API i can usually get cool stuff happening with quickly.

Stripe and Mailgun and Twitter are some of the best documented, clearest to use APIs. The Google Maps API i can usually get cool stuff happening with quickly. My favorites overall are probably Sunlight labs APIs though: http://services.sunlightlabs.com/ http://services.sunlightlabs.com/