I was searching for a method to put bookshare ebooks onto my Kindle. It seems to be asked a bit so I wanted to post a solution I found. In the comments section of this page, anonymous posts how to do it with calibre
http://bdmtech.blogspot.com/2011/06/...bookshare.html
I've reposted his/her comment here
AnonymousMay 4, 2012 5:04 PM
It is actually easier than this by one step. Instead of creating a PDF, simply save the file from your browser, changing the file extension from .xml to .html in the save dialog box. Be sure to leave the default option of the file format as "web page, complete."
Then simply open it in Calibre and convert to your preferred format.