Google Toolbar version 5.0.2009.0324b for Firefox 2+ version users is available now for download (updated on April 13,2009).As many of us know Google Toolbar had introduced the famous Google Chrome feature viz., Most Visited Sites access in the toolbar, the same feature is obviously available in this version too.
For a complete list of features of Google Toolbar, visit Google toolbar page
You can also add your custom buttons to Toolbar by choosing from Google Toolbar Button Gallery
Firefox 2+ Users, install Google Toolbar 5.0.2009.0324 [Beta Version] from this Firefox add-on page