Google has this nice feature: select "some text" in a web page, right-click, and you see a menu item:
Search current search engine for "some text"When you select the menu item, Firefox performs the search and presents the results in a new tab.
This behavior is really useful. For example, when you're reading a forum post in which someone cites an API or software product you've never heard of, you can go off and learn more about the citation without losing your place in the forum.
WebKit (and Safari3?) have a similar menu item. Of course, unless you've installed some 3rd-party extensions the search engine is always Google. But the really unfortunate thing is that the search results replace the current page.
Maybe there's a magic key combination which lets you override this behavior, but I haven't found it yet. It sure would be nice if Safari implemented this feature in the same way as Firefox.