ShareThis for Firefox (Mac)

ShareThis is a toolbar button that provides one-click sharing of online content directly to IM, social networks, and e-mail, without having to leave the source page. Sharing to AIM, MySpace and Facebook requires free registration which walks you through creating a mashed up contact list. Once you register, ShareThis will post directly to MySpace comments and Facebook walls without having to log into each site or visit each friend's profile. All of your shares are also saved to your personal Sharebox where you can view them and easily share them again. You can share anything to up to 5 e-mail addresses at a time without having to register.

Requirements:

Mac OS X 10.4, Mozilla Firefox 2