How to display pop-up window?

Hi. I’m wondering how (or if) I can accomplish the following with WordPress. I’d like it to have each of my weblog posts have a link that, when clicked, opens up a pop-up window that displays a few words of text. More specifically, how can I most easily do the following:

1) Create a pop-up window from within a post?
2) Control/edit the text content of the pop-ups from a text entry box within WordPress’s post.php (just like the way you enter text into your Post)?

Finally, before I do this, does anyone know of a plugin that already accomplishes something like this, so that I wouldn’t have to reinvent the wheel?

Thanks in advance,
Amir