I was thinking about a similar implementation recently... I think that the bookmarks module has pretty much all the needed functionality.
My scenario works like this:
1. The user has to activate his bookmarks first...
2. He sets up different folders (categories) to his personal bookmarks tree.
3. When a bboard thread gets mailed to him, he would see an ordered list of links that represent his bookmark folders at the bottom of the email. Maybe right above the link to the thread and the unsubscribe link.
4. The user could now decide where to save this particular thread in his bookmarks. He would only have to press the right "folder link".
5. The users could additionally add some more internal and external links via the bookmarks user interface of the openacs site...
6. I also thought about a javascript link that the user can add to the bookmarks of his browser. Whenever he wants to add the page that he is currently surfing to his openacs bookmarks tree, he would just click on that bookmark and a popup would appear. After he logged into the openacs site via this popup he would see his folder tree and a field to enter the name of the page, a description, a ranking etc...
http://www.blink.it has this functionality and it's pretty useful. It is pretty easy to implement, too!!!
