When you hover over a link, SwiftPreview shows a graphic preview of the page linked, and the extension is fully customizable so you can keep it from being annoying.

Chrome: HoverReader, once installed, lets you hover over a link to a news article to see a pop-up display of an article preview or its full-text before you click.

Wikipedia has just introduced a new preview function: If you hover the mouse cursor over a link to another Wikipedia page, you will get a peek of the article, including the first few sentences and ...