If you need to quickly build REST APIs over existing data in excel sheets, RDBMS, NoSQL data stores; then the DreamFactory toolkit is immensely helpful.
DreamFactory is available under the Apache 2 license and you can host it on your public/private cloud platforms. Just with a few clicks, you will have a complete secure API service available to perform CRUD operations on your data. DreamFactory runs on the Apache LAMP stack ((Linux, Apache, MySQL, PHP/Perl/Python).
Besides generating the APIs, DreamFactory can also dynamically generate a Client SDK for HTML5 frameworks like jQuery, AngularJS, and Sencha, and a code library for native clients like iOS, Windows 8, and Android.
DreamFactory also has a toolkit to convert your SOAP webservices into REST APIs - https://www.dreamfactory.com/resources/video/how-turn-any-soap-web-service-rest-api/
It also has a cool feature called DataMesh wherein we can create virtual foreign key relationships between tables in the same database or between completely different databases without altering your schema or writing any code. Create, read, update, or delete objects and related objects with a single API call.
DreamFactory also automatically creates Swagger API documentation and has basic API Management capabilities built in (e.g. rate limiting)