Jason - Infinitely hackable mobile client
Nacapi - Turn your JSON into a restful API
Paychex - Are you in need of payroll services, HR services, 401(k) and benefits administration, or more? No matter the size of your business, Paychex can help.
JsonAPI - Application and Data, Languages & Frameworks, and Query Languages
Replicon - Replicon is a unified time-tracking software that elevates time as a strategic asset within an organization, to improve operational productivity, performance, profitability, and compliance.
ReqRes - A hosted REST-API ready to respond to your AJAX requests.