APITable is described as 'From Table ? JSON'. There are more than 10 alternatives to APITable, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and iPad. The best alternative is Google Drive - Sheets, which is free. Other great sites and apps similar to APITable are Airtable (Freemium), soapUI (Free, Open Source), Sheetgo (Freemium) and Beeceptor (Freemium).
Airtable is the easy but powerful organizational tool that works exactly the way you want. It's as fast and flexible as a spreadsheet, but offers a refreshingly clean, modern way to organize and collaborate on everything.
SOAP/REST Mock Service is a simple configurable framework to mock out SOAP or RESTful (or "REST-like") webservices. It's main goal is to support automated integration testing of applications that integrate with 3rd party webservices.