As someone who does a lot of research in many fields it's important for me to be able to search for terms on many websites....For an example...lets say I just read an article that mentioned the String Theory.

 With this little ie add-on software I can highlight the text "String Theory", right click and go to the menu pop-up to do a search from any site that has already been preprogrammed into my lists such as google, wikipedia.org, a dictionary, send the selection as an email, I can do a web search, an image search, a blog search, an usenet search, a reference search, and more.
Each heading has many subheadings from which to search from Plus it's totally customizable so let's say you search Google Videos a lot, you can set it up so that you can highlight the text that you want to search, right click and chose the google video search that you customized into your menu pop-up and a webpage will pop up with all the google videos with the words that you highlighted, it's that easy.

I can't recommend this program enough for any serious researcher on the amount of time it saves.

In my opinion it's a must have for any serious researcher that uses the internet.

Here is the link to the download site, they have well explained faq's that will help walk you through the customization process.

http://www.optimussw.com/theyrealive/download.html