Google Toolbar for Firefox can no longer be downloaded.
Google Toolbar for Firefox extends the browser even more allowing you to share pages directly, write side-wikis about the pages you are viewing, auto-translate pages instantly in Firefox and much more.
Other features include a multi-language spell check, Google search box and a built-in auto-filler for forms and other fields. You can even check your Gmail via the toolbar without having to open your inbox within Firefox. Other add-ons you may choose to select or deselect is a pagerank tool. The number of buttons you can add is a bit overwhelming in fact and can soon leave Firefox looking bloated and cluttered.
Most worryingly however is the memory leak associated with Google Toolbar. I was using the latest version of Firefox (version 3.6.3) and found that at random moments, it leaks memory terribly meaning that Firefox simply freezes with the spinning wheel of death crashing the browser. The only solution is to deactivate or uninstall it in your Add-Ons menu and wait until Mozilla and Google find a solution.
Google Toolbar is designed to increase productivity and make life easier although the terrible memory leak with the latest version of Firefox means using it can be more trouble than it's worth.