The PivotalTracker Go SDK by Ondřej Kupka interacts with the API to access data for project management. Usage and documentation available. Complete pivotal package at https://godoc.org/github.com/salsita/go-pivotaltracker/v5/pivotal
DoneDone, issue tracking service, offers the DoneDone API that enables developers to include DoneDone's feature set via existing workflows and third party applications. DoneDone's premier goal is to streamline and simplify projects and eliminate the use of spreadsheets, sticky notes, email chains and other traditional forms of cumbersome notes and reminders.
In a first for US mobile carriers, Sprint has opened up an initial set of REST services for developers to play with for free at their new developer sandbox. With these services (Sprint API profile), developers can now access location, simple presence, and send SMS messages to Sprint handsets without requiring any software installed to the device.