Wanna search using Wolfram Alpha’s impressive computational knowledge engine and do so with one click? Clickable Resources have created a WolframAlpha Search Plugin for – Firefox, of course🙂 . Click on the link to install the plugin, which will add the Wolfram Alpha option to your Firefox search box.
Aparently you can do the same thing in Opera as one comment on Lifehacker suggests: “Go to tools->preferences->search. Click on add. Enter a name like &Wolfram|Alpha (by using the ampersand, the icon of the site will be used as searchicon), enter a keyword like wa (so you can enter wa [here your searchquery] in the urlbar to search) and enter [www.wolframalpha.com] as address.”