Try Google specific website search by adding
site: option to the search string, for example:
The Avengers site:imdb.com
That will search within the specified site. Very powerful option.
You can also search within multiple websites, to do that use the operator
The Avengers site:imdb.com OR site:boxofficemojo.com
If you want to search many websites at the same time, you can use Google's Custom Search. Using this tool Google will create a custom search tool for you where you define which websites to search and a lot of other things using a control panel. You can use the page provided by Google or you can even embed the search tool within your own website if you wish.