The first user script I ever wrote was called Butler. It adds functionality to Google search results. To see a brief description of the functionality that Butler offers, visit the Butler home page. To install it, right-click (Control-click on a Mac) the link titled "Download version 0.3." From the context menu, select "Install User Script...."
Greasemonkey pops up a dialog titled "Install User Script," displaying the name of the script you are about to install (Butler), a brief description of what the script does, and a list of included and excluded pages. All of this information is taken from the script itself, as we'll see in a moment. (See Figure 2.)
Figure 2: Install user script
Click OK to install the Butler user script. If all went well, Greasemonkey displays the following alert: "Success! Refresh page to see changes."
Now, search for something in Google. In the search results page, there is a line at the top of the results that says "Try your search on Yahoo, Ask Jeeves, AlltheWeb, ...," [figure 3]. There is also a banner along the top that says "Enhanced by Butler." All of these options were added by the Butler user script. (See Figure 3.)
In addition to web search results, Butler also alters image search results by adding links to a variety of image search engines (See Figure 4). It even adds links in Froogle to other product comparison and shopping sites. (See Figure 5.)