1) You may want functionality similar to saved topics but with subforums for organization ("saved topics" has no subforums, it's just a list). You can let people add existing topics from your directory into their personal topics list and its subforums using this template code (a good place to put it is in the topic bit, Admin Panel -> Themes -> Manage Templates -> "Sub-Templates" -> "Topic Bit"):
<IF {TID} does not contain albums>
<form action="albums.php?add={LINKID}" method="post">
Add to <select name="subalbumid">{THISMEMBERALBUMLIST}</select>
<input type="submit" value="Add" >
</form>
</IF>
<form action="albums.php?add={LINKID}" method="post">
Add to <select name="subalbumid">{THISMEMBERALBUMLIST}</select>
<input type="submit" value="Add" >
</form>
</IF>
Or if you don't want to involve subforums a simple link:
<a href="albums.php?add={LINKID}">Add this topic to list</a>
To allow people to remove a topic from their list, place this by it:
<IF {TID} contains albums><a href="albums.php?todo=remove&linkid={LINKID}&catid={LINKCATID}">Remove</a></IF>
Thanks to the conditionals, you can put these in the topic bit and the add form will only show outside of the personal topics list while the remove link will only show inside the personal topics list.
2) You may want to let people add new topics that aren't in the directory. This is mostly useful for WSN Gallery, where members can have their own personal albums of their own images which aren't mixed with the site's images (you can even use your WSN Gallery as an add-on for a forum giving forum members each a gallery, when integrated with the forum member system). You may perhaps find use for it in the other scripts too.