Go to options, manage search engines and add this as the URL (between the ><) :-

>http://www.google.com/search?btnI=I%27m+Feeling+Lucky&ie=UTF-8&oe=UTF-8&q=%s<

Name it what you want, Keyword what you want - I use lucky but if you use it regularly you could just use l.
To use it just type 'l example' in the omnibox, where example is your search word (or in my case I type 'lucky example' - without the quotes of course)

Most types of search can be added in this way, just determine the search string by carrying out a search then replace the search word with %s.

Hope this helps.