I'm trying out Chrome, but I use this Firefox feature all the time so I strongly feel its absence. I've searched Extensions and Google in general, but couldn't find anything and don't even know if it's possible to create such an extension. Important: I'm not interested in extensions that require me to click anything to activate the different searches. The important part is it all happens in the URL bar.
If you don't know what this Firefox feature does, briefly: you can assign a keyword to a bookmark and embed
%s in the URL. Then, from the URL bar (not the search bar), you can type the keyword and then one or more words to replace
For example, if you create a bookmark with URL: "http://www.imdb.com/find?s=all&q=%s" and keyword "imdb". Then in the URL bar, you would just type: "imdb young frankenstein" and it will send you to: "http://www.imdb.com/find?s=all&q=young+frankenstein".