I'm not sure if this is new to anyone else, but I just found this yesterday and have already been using it continuously. It's DownForEveryoneorJustMe.com
. You go to the site, enter the URL you want to check and it'll tell you if the server is down for everyone or you're the only one having the problem (evil corporate employer network filters). It should be a required feature for all those social network users users *cough-twitter-cough*.
Also, because I'm lazy I built a bookmarklet so I don't have to go to the site and enter the url myself every time.
I hope this is as helpful to everyone else.