Are you sure it doesn't work? I've found all the bookmarklets I have work for me (haven't tried readability though). But the way you get it, is by going to the website, creating your settings and then tap and hold on the bookmarklet and add it to your bookmarks.

And then to use it, you click on your bookmarks, click on the bookmarklet. I personally have a bunch of them saved into a bookmarklet folder.