Google Toolbar
 

Not really a software...However, a plugin to many famous browsers out there.

It's a great tool which gives you live PR's of various sites. Has the search bar on it *duh* ...Many other stuff like Spell Check, Auto Fille, Auto Link (love it), also, another feature which is kinda tough to explain.

Do you use it? If so, what is the main feature that you use the most? Why?

Please post. Thank you. :)

Never used it, I'm going to try either that or Alexa toolbar though in the future. They can get annoying sometimes so that's why I've tried to stay away from them as much as possible.