This could be the coolest online service for People who Blog and Twitter too. Dingitsup ( Via FiredBeef ) service allows you to get notified on twiiter when your site comes back again or gets down. I am emphasizing on gets back again because this will save you a lot of time from not doing refresh or hitting the enter button again and again.
This services also can mail or text you when the site comes back. I had talked about the twitter thing first because other services like Uptime Party ( which monitros your site every hour ) and to check if the site is just down for you alone but integration with twitter is just awesome.