Google Toolbar for IE has been upgraded with new features and enhancement.

Link:
http://toolbar.google.com

Also, if you want an Open Source solution then check out GoogleBar (Firefox only)

Check out these posts too:

  1. Google Toolbar for Firefox v2.0 Beta
  2. If you build it they will come……..well hopefully.
  3. New MSN Toolbar, now with more Bing
  4. IE Developer toolbar
  5. Google Toolbar 3 beta
  6. Google Suggest for Firefox
  7. Internet Developer Toolbar beta 1 refresh