Jed Schmidt, creator of Pastebud, says they have been testing it for about a week and they are now "putting the finishing touches on the web site before launch".
Pastebud does not require any application to be installed. It works using two bookmarks in Safari. When viewing a webpage you click the bookmark entitled COPY and it will reload the page giving you the ability to select text. For this newly loaded page you can either open a new message with the selected text as the body, or you can copy the text to the 'clipboard' and use another bookmark entitled PASTE to paste it into a text field on another webpage.
You can watch it in action below...