Just looked to standard Facebook bookmarklet and found that it does not allow to select some text and share it with friends. As I would like to be able to do this and as far as I have already implemented similar twitter bookmarklet, I decided to create and publish Facebook one too. So, you can dragg the following link to your bookmark bar:
To post something to Facebook just select the text on any page including Facebook pages and click the bookmarklet on your bokmark bar.
Feel free to recommend this bookmarklet to your friends and you can test it on this page as well.