If you use Firefox 2, you've noticed that the search box shows suggestions for Google, Yahoo and Answers.com. Google's suggestions are useful if you want to type less, but also if you want to use Google Calculator. Type math expressions, unit conversions, constants and the answer appears in the list of suggestions. It's handy that you can just copy the result and get on with your work.
Firefox uses this URL to retrieve the suggestions: http://suggestqueries.google.com/complete/search?output=firefox&qu=[query]. Note that Google Toolbar for Internet Explorer doesn't show expression results.
{ Via Blogoscoped. }
Related:
10 uses for Google Suggest
Yahoo instant calculator