'Google Talk', and 'Flash Mute'

Google Talk

We recommend this highly! Every Saturday for the last 6 weeks we've spent 4 or more hours on Google Talk with a friend in Australia working on a project. We experience no lost connections and great sound quality. Google Talk beats every other Internet phone service we've seen!

http://www.google.com/talk/

Flash Mute

FlashMute is a tool which allows you to mute / unmute Flash Movies loaded in a browser exclusively -- and even all other the sounds produced by the browser.

http://www.indev.no/?p=projects#flashmute