I tinker often with external webpages and sometimes miss having jQuery available there. Then I use the following link as a bookmarklet, which just loads jQuery into the active page:

Right click on the button above, add to your bookmarks and you’ll never have to go on your explorations without jQuery on Chrome.

If you have a Bookmark Toolbar, then you can just click and drag there as well.

Note: Doesn’t work on Firefox 29.

How it works

It executes the following code on the active page:

!function(){
    var s=document.createElement('script'); 
    s.src='//code.jquery.com/jquery-1.11.0.min.js'; 
    document.body.appendChild(s)
}()

This fetches and loads jQuery on the page.