Googlepedia is a nice Firefox add-on for those who always need to know more about everything. Every time you perform a Google search it will display Wikipedia articles related to the keywords you entered.

The articles are shown along a column on the right side of the web browser. This can sometimes break Google's layout, but unfortunately you can't customize its width. There's a link to optionally shrink or expand the results so that you can read the article in a more comfortable way.

On the downside, displayed articles can sometimes be a bit redundant, as Wikipedia itself is often among the first places in Google's results. In any case it's an easy way to obtain more information about a given topic without having to type in anything.