Web Application/Tool Sniffer is a free, open-source, and non-commercial utility that detects and displays web applications, tools, and javascript libraries running on the websites you browse.

Once you have selected the websites you want to visit, you will be able to perform searches on each of them. You can also choose to have the application perform a search for you when a new application is launched. You can choose to set it as a default application. This means that it will be displayed in the list when a new application is launched.