Since I kinda know something about links, I feel a personal obligation to respond ;)
At the most basic level, here the admins set up a links page and users share links through MLP when they find something interesting, not to mention diaries and users' personal home pages. Sounds like you're looking for something more, though. I saw Dmoz mentioned in the earlier discussion at k5, but from what I gather you're after something which is user-based rather than editor based.
If I understand this right, here are some more things that will need to be considered: When searching and browsing most likely you would want the more popular links nearer towards the top, so users might basically be voting for links. Users would want to be able to update their links, and to be able to remove their promotion of links they no longer wish to promote, for instance if a site does a bad thing and ticks them off. If directories/categories are implemented, there'd have to be a way to create new ones and alert users to reclassify some of their links.
Kind of a big project, but it's a neat idea. Even if it's not right for k5, it would be interesting to see on its own site. Heck, it's something that I might even link to. =)
