Possible suggestions:

i) as suggested the add a link and an easy way to sugggest this link for inclusion in the directory. I also wonder if this could be somehow used as the basis of a bulk link adder?
ii) make mylinks public or hidden dependant on user choice. So other people can see your link list if you want.
iii) a way to import, export links to and from a computer so people can download them. If you go for option i) an easy way for someone to upload their list of links from a text file (perhaps this text file could be generated from their IE shortcuts but don't know about that one).
iv) A way for a user to add their own comments to saved links. This would require a table like:

ID, LinkId, UserID, Comment

the comment could then be displayed either instead of or beneath the description. I would imagine it quite likely that people might want to use a different description for their saved links.
v) Admin limits on the number of links storable per user.

All i can think of, you seem to have most of it covered.

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