Google toolbar is a BHO ( Browser helper object ) which has pagerank display and other unique features, Some features of google toolbar are autolink, highlight button, blog this button, pagerank display , news button, backlinks button, auto fill, spell checker etc,

Auto Link: Auto link automatically changes certain part of the text in a site you browser into hyperlinks to other sites, This feature sometimes changes the links and points to specific maps or to other sites like amazon,

Pagerank Display: Pagerank is the technology of google in judging a quality of a site based on the links pointing to that pagerank, The more the links and the better quality the links are the pagerank passed with be more, Pagerank display helps in judging the quality of a site to a certain extent,

highlight button: Highlight Button helps in highlighting certain text specified in the search box,

Search Box: helps in searching the web,

Auto Fill: Helps in filling out online forms much faster,

Yahoo, MSN, A9, Teoma all have their unique toolbars,

Search engine toolbars helps in search engine optimization in various ways, options like the highlight button helps in judging the keyword density and keyword distribution of a page, Pagerank display helps in determining the pagerank of a site etc,

                                Earthlink Netscape Netvouz RawSugar Shadows Sphinn StumbleUpon Yahoo MyWeb