Scheduled tasks - GNOME GUI for configuring a users' cron (automatic jobs). Some of its features are:
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Kana Reminder - Kana Reminder is a program which can be used to set a reminder to be triggered at a specified time.
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
Auto Mail Sender - Auto Mail Sender Standard Edition official page. A powerful and easy-to-use eMail scheduler.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface