Tired of physical signatures interrupting your document workflows? HelloSign released the HelloSign API that allows developers to integrate eSignatures into websites, apps, or company processes. HelloSign's creators were first bothered by paper's inefficiency and wastefulness, and the irritation led to HelloFax.
Diffbot is one of the coolest new ideas on the internet. The service brings monitoring to the web in a new and interesting way. The company is just about to release a whole slew of projects built on its collection of Diffbot APIs for following changes to web pages and RSS, as well as extracting clean text from websites.