BCX.RB is a full-fledged Ruby client that wraps the Basecamp Next API. Though not officially built by Basecamp's provider, 37Signals, BCX.RB is endorsed by Basecamp on their GitHub channel and developer site. Though it is usable, the wrapper is lacking endpoints and thus it's coverage of the Basecamp API is partially incomplete. Community contribution is encouraged. The following API resources are supported and have been tested using the wrapper: People, Projects, Todolists, Todos, Accesses, & Authorization.
Celoxis is both an online and installable project management platform integreted with Microsoft Outlook, iCal, Google Calendar, and Salesforce.com, among others. Celoxis explains the Celoxis API in a way that suggests they want you to be able to use it easily.
Seven APIs have been added to the ProgrammableWeb directory in categories including Cryptocurrency, Messaging, and Collaboration. Highlights include the Monday.com API for collaborative workflow automation and the Flume API for tracking water usage in homes. Here's a rundown of the latest additions.