Wolfram Alpha is very much in talk after it was made available to public. Some say that it is a Google Killer, while some say that its not up to Google. If you want to get the features of both Google and Wolfram Alpha, then here is a simple Firefox add-on which does this job well. This experimental add-on lets you to search in Google and at the time it also shows the results from Wolfram Alpha.
The Wolfram Alpha results are shown in the right hand side of the page pushing the Google results. Overall the results of the add-on looks good.
There is also a link to open the Wolfram results in another tab from the search. This is very useful if you want to get the information from both search engines. The only issue with the add-on is that if the Wolfram Alpha results are big, then it might cut off the bottom portion as the Google search is set to 10 results per page.
Currently this add-on is an experimental one, we might see more features in the coming versions.