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:

    var s=document.createElement('script'); 

This fetches and loads jQuery on the page.