Webhooks by Zapier - Move Your Data Instantly With Webhooks
TexturePacker - Texture Packer is hands down the best sprite sheet generation tool on the market.
Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.
Free Texture Packer - Free Texture Packer is an open source tool that allows you to pack multiple images into one atlas for you games or sites.
Hookdeck - Hookdeck makes it simple to build and deploy reliable, testable, and debuggable applications that rely on webhooks.
Sprite Monkey - Small and fast but still full-featured sprite sheet editor.