Google Toolbar for Firefox

This highly configurable toolbar integrates with Google Web History, your Google Account, Blogger, Google Bookmarks, Gmail, Google Docs & Spreadsheets (you can configure it to open/edit files in a browser window for you, no MS Office required); and provides you with a detailed record of your Google searches and web page visits. Allows you to set your Gmail account as the default mailto: client. A very handy toolbar, but be sure you read the documentation thoroughly so that you are aware of the privacy implications inherent in recording your every move on the Internet. Update: If you add the Google Calendar button to it, you can use it to add events to your calendar without opening a page. Clicking the Calendar button opens your Calendar in a new tab. Similarly with the Docs&Spreadsheets button.  Update: if you install it in Firefox Portable, it may not remember new buttons that you install to it when Firefox is restarted.  Please add your comment if you find a workaround to this.