Our API directory now includes 88 project management APIs. The newest is the Trajectory API. The most popular, in terms of mashups, is the Basecamp API. We list 14 Basecamp mashups. Below you'll find some more stats from the directory, including the entire list of project management APIs.
As business computing migrates to SaaS applications, developers must address the problem of the data silos the software creates. APIs let you move data in and out of these online applications but, they present a new set of problems: managing data in several applications using several APIs.
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.