Timetaco lets you easily create your own countdown with custom background + Unsplash and push notifications!
Countdown Screensaver is a Mac OS X screensaver to countdown to your big day. Minimalistic design, useful, and 100% free.
Hurry is an app for Android that creates beautiful countdowns to the days and events that you look forward to in the form of beautiful widgets.
TikTok is a customizable countdown timer that lives in your Chrome browser.