After Google released Chrome, Google Toolbar's development slowed down. That's because Google Toolbar is no longer the primary vehicle for adding browser features and Google mostly focused on improving Chrome.
Google Toolbar 8 is a completely new version of Google's add-on that was available as part of Google Labs. "Google Toolbar 8 is actually built and runs on top of the Google Chrome Frame platform. This means that Toolbar 8 will run more like a web app in that it can be customized and updated much more frequently and easily. It also means that Google Chrome Frame is installed at the time of Toolbar 8 installation," explains Google.
The new version of Google's toolbar only works in Internet Explorer right now and it doesn't include all the features that are currently available in the latest public version. Google included some new features: buttons for the most visited sites, Google Dictionary integration and Google Instant. "Google Toolbar displays up to seven of your most visited sites as buttons. Click on a button to go directly to its site. When you download the new Google Toolbar your toolbar will display buttons for Gmail, Google Calendar, Google Docs, Youtube, Google News, Google Reader and Google Tasks by default."