Is there an online count down timer/alarm clock that gives you nudge when a set time is up?
I do not want it to play a sound, but rather give me a notification that I can see (like when you get a msn message)
Check out Aero Timer extension for Chrome
You can either do a count down or set a time for the alarm to go off. The extension icon shakes when the time is up and it also sends you a desktop notification. The only down side is that does play a sound as well, which at the moment, you cannot turn off.
http://www.timer-tab.com will do that on Google Chrome / Chromium. Check out the options.
Note that you can't disable sound notification.
Disclosure: I wrote this web app.