DING, IT’S UP is a fairly new service that repeatedly pings a website you specify and lets you know when it goes down, or when it comes back up. It can send you an alert via email or by Twitter.
Want to know when Twitter comes back after their most recent downtime? Tell Ding It’s Up to send you an email when the site becomes available again.
Would you like to know if your website has some unexpected downtime? Just input your domain name and pick either a Twitter or email notification, whichever will get to you sooner.
The site is very simple, just the bare essentials. Not even a logo. Just a simple form to fill out, and a paragraph of text under it.
Just don’t try to get a Twitter notification of when Twitter.com goes down. It won’t work very well. 
