Trish,
I'm not understanding how you feel a wiki could replace links.
Fundamentally Wiki pages are rich text pages which can edited by site users. In the case of a group, that would mean the group members (if permitted).
So, members could write descriptions and include links with those descriptions. So a collection of links could be written as just a list of paragraphs, each with a link in it. An additional wiki page, linked on this page, serves as a "sub-folder" and provides a way to organize the links into collections.
But where a simple wiki falls short compared to the kind of links feature Yahoo Groups has is in the organization of the links - in a simple wiki it would all be manual, no sort by contribution date, versus alphabetic by title, versus "who". Likewise, the access control is all or nothing - if members can edit the wiki they can edit anyone else's supplied links as well as their own.
-- Shal