Proposed solution: Using page scores
Assume that pages can be scored and ranked. The system will then use these rankings to focus navigation for the user. The ranking for each page is calculated in relation to the ranking of that page and of adjacent or nearby pages.
For instance, you could have a thresholded RecentChanges on a Wiki that wouldn't display a change unless its fuzzy rating was greater than some value, say, 0.5.
This automates some of the mental work many users do already with RecentChanges, helps build PersonalCategories more dynamically and fluidly, and allows for random information at the "fringe" to come in that may be of interest.
Proposed scoring mechanism: manual scoring
Have users make personal ratings for any pages based on their interest for those pages (say on a scale from 0 to 10).
Proposed scoring mechanism: automatic scoring based on your homepage
Instead of rating pages (which I find rather cumbersome), let us take advantage of information already available: People's homepages often link to interesting pages on the wiki. My homepage links to my favorite IndexingScheme, for example. Therefore, if a user has set his UserName, all pages linked to from the homepage are assigned a score X. Optionally, pages reachable by another level of indirection (two links away from the homepage) are also assigned a score X. This allows me to link to SunirShah's homepage, and then all the pages he likes will get a good score, too. Or I could link to the WikiNoise interest group homepage, giving the pages they link to a higher score.
Don't forget that scoring is voting, and VotingIsEvil.