I'm defining best as:
- At least one very good answer with code included (or explained)
- Answer should cater to users of any level of skill (ie. don't expect a math background)
- The question should cater to a useful topic (not 'I've got error X with platform Y')
- The topic should be important, that even people not specifically looking for it should find it
- The topic should be a popular problem or question, not a fringe use-case
Now before you all jump on me saying "there's no need for such a thing!", let me reason why such a list could be useful. You're a mediocre developer with no specific problem on your mind. You browse through the top voted questions on SO, but you find that it's not categorised in any specific manner (although you can filter, and get somewhere), but eventually you get bored scrolling through lists of varied questions and leave. What if you had a site that listed useful questions by category? Let's say you visited Best of Stack Exchange, the "Stack Overflow" section and clicked on the category "Databases". You would see a long list of categorised database questions and answers that you could easily jump to if you wanted to know about any. This way we're indexing the best of each Stack Exchange site so users of any skill level can leverage the massive knowledge stored deep within the wells of each website. Also, many good questions that have been answered fairly well are not voted highly, and therefore gets mixed up with all the other questions on the sort-by-vote section even if you filter by a tag. And when questions are organized under a well-defined category structure you could narrow down to your interests quickly.