- Request Bin - AKA Postb.in, the original-ish
- Mailgun's request bin
- https://www.runscope.com] - commercial tool
- http://respondto.it/ (RespondToIt) - allows mocking of responses
- http://webhookapp.com/ (WebHookApp) - webhook receiver
- http://httpbin.org/ (HTTPBin) - Another Runscope util; endpoint/receiver more general HTTP client debugging
- https://ngrok.com/ (NGrok) - native desktop APP which creates public webhook endpoints from behind firewall and allows inspection and replays from local web browser. VERY sweet.
- http://www.zapier.com/](Zapier) - configurably connect webhooks to other services, including email output.
- HurlIt
- APIKitchen
- APIBin
- http://www.getpostman.com/ (Postman) - Chrome app
- http://ditchnet.org/httpclient/ (Mac HTTPClient) - nice GUI
- https://npmjs.org/package/http-console2 (HTTPConsole2) - node CLI / REPL for HTTP requests
- https://github.com/fictivekin/webshell (WebShell) - another HTTP REPL
- https://github.com/jbittel/httpry (HTTPry) - sort of specialized tcpdump/ngrep
- https://chrome.google.com/webstore/detail/dev-http-client/aejoelaoggembcahagimdiliamlcdmfm?hl=en (Dev HTTP Client) - one of many Chrome and Firefox Extensions