It seems clear that people use Stack Overflow-based sites in several different, distinct ways:
a) they're looking for help with a problem;
b) they want to ask a question;
c) they want to answer questions or contribute in other ways, such as by voting.
While group 'a' can find what they are looking for using search, and group 'b' just clicks the 'Ask Question' button, people in group 'c' are perhaps less well served.
I'm in group 'c'. I can see a list of unanswered questions with a particular tag, say windows-xp, but that's a long list. Whenever I go to that list, I see the same basic list of questions I saw last time I went there. Sure, questions shuffle up and down the list, new questions arrive and answered questions disappear, but basically it's the same list as last time. I don't want to page past those same questions to get to the ones I haven't seen yet, every time I visit. As a result, after a few pages I don't bother to continue. So there are hundreds of questions lower down in the list that I will probably never see, and some of which I might well be able to answer.
One possible solution would be to add basic, personal flagging. Below each question there would be a small list of flags, including: track and ignore. Clicking 'track' would add that question to my 'tracking list', which I could then show separately. I would use this to flag questions I might be able to answer, or questions I'm interested in for some other reason. Clicking 'ignore' would add that question to my 'ignore list' which I could then show separately, but - more importantly - it would also prevent the question from being displayed in the regular question list. If I'm not interested in a question or I'm unable to answer it, clicking 'ignore' would remove it from view and allow questions lower down the list to appear. Yes, I'm aware that any way you slice it, this will involve storing a lot of new data, but it would be worthwhile, in my opinion, because it would make SO-based sites much more usable - at least for people like me who want to answer questions.