Google Homepage Reloaded is a greasemonkey script, which gives users the ability to click Google logo on Google homepage to change the website they search.

Revert recent changes on Google’s homepage and remove S-U-P-E-R-sized search box and other elements with this greasemonkey script.

DirectPic is a tiny greasemonkey script which opens images directly from the Google Image search result page.

There are several ways to integrate other search engines with Google result page. But, Matt Cutts has created a greasemonkey script for adding other search tools in the same manner as you may have seen in some April fool prank screenshots.