Unity Web History Lens allows a user to search the websites he has visited on his computer. It currently supports Chrome/ium and Firefox and has been developed by same developer who provided updated Ask Ubuntu and Reddit Lens for Ubuntu 11.10 in his PPA.
The PPA also includes Clementine, Rhythmbox and Guayadeque scopes for Unity Music Lens. These scopes will allow you to browse your music library and directly play a song/album form Unity dash.
To add the PPA and install them run the commands below:
sudo add-apt-repository ppa:markjtully/ppa
sudo apt-get update
sudo apt-get install unity-web-history-lens clementine-scope rhythmbox-scope guayadeque-scope